


A Murder Takes Manhatten

by Jayie_The_Hufflepuff



Series: The Castle and Eleventh Doctor Adventures [1]
Category: Castle, Doctor Who (2005)
Genre: Aliens, Angst, Banter, F/M, Friendship, Gen, Hurt/Comfort, Murder, OC alien species, mostly from the Doctor
Language: English
Status: Completed
Published: 2013-02-16
Updated: 2013-03-07
Packaged: 2017-11-29 11:17:30
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 11
Words: 35,672
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/686351
Author URL: https://archiveofourown.org/users/Jayie_The_Hufflepuff/pseuds/Jayie_The_Hufflepuff
Summary: <blockquote class="userstuff">
              <p>It seems like just another case for Castle and Beckett, until a man in a bow-tie tries to break into their crime scene. Can the Doctor and River Song help the crime-fighting duo solve a murder and save the world? Or is there more going on than any of them can guess? Season 5 Pre-Target and Hunt for Castle, Season 7 Pre-Angels for Doctor Who.</p>
            </blockquote>





	1. Doctor who?

**Summary for the Chapter:**

> A body is discovered, and a man in a bow-tie tries to find out more.

*Yeah, yeah, I know, I'm a horrible person for getting sidetracked from my main fics again, but I'll get back to then, I promise. Oh, also, I know absolutely zip about forensics or just... science in general, so if anything in here looks completely made up or misused... that's probably because it is. Sorry. Serves me right for trying to write a Sci-Fi fic I suppose, but I really felt like doing a Castle/Doctor Who crossover. Nor do I know anything about life in New York City, so most of that's made up as well. So... enjoy? Oh, and this is the Eleventh Doctor by the way, sometime after The God Complex but before Angels Take Manhattan. As for Castle, it takes place at some time in Season Five after Alexis goes off to college, but the interaction between them is a bit like earlier series, sorry about that. If you like you can ignore them talking about Alexis being at college and pretend its in seasons two or three or something.*

     Sometimes Castle believed the wild theories he came up with, and sometimes he just said them because he wished they were true. Life was more exciting when you let yourself fantasize about CIA conspiracies and psychics. And besides, his theories drove Beckett up the wall, which was incentive in itself. But he never, ever could have seen coming the one time he turned out to be _right_.

     "Ah, Detective Beckett."

     The brunette detective turned to face him as he extended her coffee out. She accepted the cup with a quick smile, which Castle warmly returned. "You took your time," she observed drily.

     Castle shrugged good-naturedly. "Alexis popped by, I got held up." He let his gaze sweep over the crime scene. They were outside a parking garage, with yellow tape cutting off most of the area and the familiar swarm of cops and CSU hurrying about.

     Beckett lifted the tape to let Castle through. "Isn't she doing that kind of often?" she asked curiously.

     Castle's face fell. "What 's wrong with my daughter coming home?" he asked in an affronted tone.

     Beckett rolled her eyes. "She's in college, Castle," she pointed out as they approached the crime scene. "I'm just surprised she's going back and forth so often. But I guess it does make sense."

     Castle puffed up a bit, his pride restored. "That's what I thought."

     "After all, there's free laundry at your place."

     His face fell as quickly as before. He threw his girlfriend an injured look, muttering darkly.

     Beckett tried and failed to hide a smirk, then turned to the CSU team gathered around the body. 

     "Alright Lanie, what have we got?"

     The medical examiner was crouched over the body of a man. He was laid out on his back, his head resting to one side and his arms and legs thrown about awkwardly. Probably from landing or being pushed to the ground, Castle reasoned. He was young, probably late twenties early thirties, with curly red hair and quite a few freckles on his narrow face. With the glasses and the tie, he had a fairly reserved bookworm look to him.

     "As far as I can tell, he's been here somewhere between eight to twelve hours, though I'll be able to narrow that down once I get him to the lab. The real interesting part,” Lanie said with more interest, “is the laceration on his throat, which I'm calling as cause of death. Take a look.” She pulled the man's shirt collar out of the way so they could better see the wound.

     A long, horizontal cut ran across the victim's throat, with blood spattered on the shirt below. More interestingly, the skin around the cut was charred and black, fading out slowly to an angry red with muted blisters. Beckett's eyebrow furrowed. “Are those burn marks?” she asked incredulously.

     Lanie nodded. “Looks like whatever cut down your victim was hot enough to  burn the flesh.”

     Beckett's eyebrows flew up in  surprise. “That badly?” Her gaze flew  over the wound again, reassessing.

     Castle's eyes widened. “A blade that was sharp enough to cut the flesh but hot enough to burn it?” At his excited tone, Lanie and Beckett turned to look at him with varying levels of interest and exasperation. Castle looked gleefully at his audience, making sure he had their attention, before announcing, “Isn't it obvious? He was killed with a lightsaber!”

     The little attention he'd been able to command was lost immediately. Beckett rolled her eyes and turned her attention back to Lanie. “Got anything else?” she asked, pointedly ignoring her partner.

     As Lanie shook her head, Ryan approached, notebook in hand. "His wallet identifies him as a Timothy Karrow, 35 years old, address 55 West 76th street, no keys on the body. He was found here this morning by some kids who work at the nearby restraunt. They got here around 6:30 this morning, found the body, called the cops. Said they've never seen him before." He gestured over to where a group of scared-looking teenagers were being questioned by another cop.

     Beckett nodded briskly. "Alright, check around to see if he might have dropped his keys. If he was parked here, maybe he worked nearby. In the meantime we'll check and see if he was reported missing and contact his family. C'mon Castle." She got to her feet and started off for the car, leaving her partner to hurry after.

     They were almost to the car when Beckett paused, eyes narrowed. Ahead of them a strange man was talking animatedly to one of the uniforms standing by the yellow tape. Beckett and Castle came up to stand beside the cop. “What's going on here?” Beckett asked calmly.

     The cop seemed grateful for the interruption. “This guy here,” he gestured irritably at the stranger, “says he's with CSU, but he's not showing me any ID.”

     Castle turned his attention to the stranger. He was wearing a brown tweed jacket with a pale undershirt and a red bow-tie, with brown hair that was swept to one side.  Currently, he was rummaging through his pockets, looking very put out when all he was able to drag out was a pair of 3D glasses and a squished bag of jelly babies. He looked up sheepishly. “I did have qualifications,” he said in a British accent, “I just seem to have misplaced it... erm, somewhere.” He gave his pockets a last glare before straightening his bow-tie nervously. Castle had to bite back a laugh at the man's eccentric appearance, but Beckett was evaluating the man carefully, her eyes narrowing at what she found. 

     “What's your name?” She asked abruptly.

     The man looked at her in surprise and a hint of irritation. “John Smith,” he offered dismissively. He drew a silver metal thing rather like a pen from his coat pocket and held it out toward the crime scene. Something green lit up on the end and it let out a _whirring_ sound. As the end snapped back into place, John held up the device, studying it closely. His face fell. “Ooo, that's not good. That's quite a bit not good.”

     Castle perked up at the sight of the weird pen-thing. “What's that?” He asked eagerly.

     John cast the cop, who still wasn't letting him through, a quick irritated glance. “This,” he said, indicating the pen-thing, “is my tool... thingy. It's doing something complicated and brilliant that's telling me that something's really very wrong with the body in there. Now, if you could just let me in...” He tried to slip past the cop, but his way was firmly blocked. With a childish pout, he backed away.

     Beckett crossed her arms, eyes still carefully evaluating the man. “Mr. Smith, if I ask anyone from CSU here, are they going to recognize you?” The man didn't respond, throwing Beckett a somewhat sullen glance. “I can call up the precinct right now and find out if you're lying, so how about you just save me a lot of time and work?”

     John glared at her with all the sullenness of a child. Finally, he admitted, “Alright, maybe that was just a clever lie, but I'm here to help, so I really don't see...”

     He was cut off as Beckett strode up to him and pulled out her handcuffs. “Alright, turn around and hands behind your back.”

     John gaped at her incredulously. “Really? You're arresting me? What for?”

     Clearly having gotten impatient with his disbelief, Beckett grabbed John by the shoulder and forced him to turn his back to her. “For attempting to break into a crime scene, obstruction of justice, false identification... you name it.” She snapped the cuffs on the man and directed him towards their car. John ducked his head and allowed himself to be shut into the backseat, glancing around the car with interest. He grinned brightly as Beckett started up the car and backed them out of the lot. “Huh, look at me arrested, never been _arrested_ before. Well, that's not true, actually very not true, but look at all this then! You've got the handcuffs, the badge, even the car! I love a good police car.”

     Beckett just rolled her eyes and ignored him, but Castle turned to face the man. “So, what's your real name?” His partner glanced at him, surprised. “Oh, come on. _John Smith_? That's the ultimate go-to fake name. There's no way that's his real name.”

     Far from trying to deny it, the man just stuck out a hand, which Castle shook bemusedly. “Quite right. I'm the Doctor.”

     Castle raised an eyebrow. “Doctor who?”

     “Just the Doctor,” the man insisted cheerfully. He leaned forward so he was between Castle and Beckett. “Look at this!" He waved the sonic screwdriver over the console of the car, grinning as the device let out a brisk _whirr_.  "It's a radio! Oh and look, that switches on the siren things!" He sniffed.  "Of course, it's got nothing on my TARDIS, but all the same, you've gotta love a flashing light."

     He reached out to poke something on the console, but Beckett sent him a glare she usually reserved for Castle. “Sit down and keep quiet,” she snapped.

     Looking a bit put out, the Doctor leaned back into his seat. Beckett turned her glare to Castle, as though blaming him for their suspect's annoying behavior. He just grinned back.

     A few minutes passed in silence. Then the Doctor took out the metal tool thing again. It let out that _whirring_ noise from before as he studied it with a furrowed brow. Castle glanced at Beckett's irritated expression, but in the end his curiosity won out. “What exactly is that?”

     The Doctor continued to study it as he answered, “This is my sonic screwdriver.” He looked up at Castle's confused expression. “It's a screwdriver... only it's sonic...” He looked down at the device again. “More importantly, it's reading low levels of tyron energy. That's defenitely not good. Tyron energy can be used for a number of things, lots of different weapons and devices, including an advanced form of energy bomb.”

     Beckett had been looking at the road ahead with exasperation at the Doctor's babbling, but at the word "bomb" she stiffened. "You're saying you think there was a bomb nearby?"

     The Doctor shook his head. "No, not nearby, the readings are too low for something that, but something there as definitely shedding Tyron energy." He adjusted his bow-tie, seemingly without even noticing what he was doing. "The problem is, humans aren't supposed to discover Tyron energy for another few thousand years, so whoever was there is either from the future or an alien, more likely alien."

     Beckett's interest dissipated immediately. She threw Castle a look that plainly said _This guy is nuts,_ which turned into a glare as she took in Castle's enraptured expression as he listened to the Doctor's words. "Listen, we're going to need your actual name."

     The man blinked in surprise. "I told you, I'm the Doctor."

     "Yeah, I got that part," Beckett said, rolling her eyes, "but Doctor who?"

     "It's just the Doctor. Why is everyone always surprised? I like 'the Doctor.'"

     The detective gave a quick glare over her shoulder. "What, it says 'The Doctor' on your birth certificate?"

     The Doctor sighed. "There is no birth certificate," he explained patiently. "You're not going to find me in any database or catalogue you have, and I'm not a citizen of any country."

     Beckett raised an eyebrow, a disbelieving smirk playing on her lips. "So  
what, you don't exist or something?" she asked.

     "Oh, I exist," the Doctor assured her cheerily, "I just don't live on Earth."

     Castle leaned forward, child-like excitement bubbling up inside him. "So where do you live then?"

     The Doctor grinned. "In my TARDIS."

     Before Castle could ask what a TARDIS was, Beckett sent him a silent glare clearly telling him to zip it, then turned back to the Doctor. "Alright, we'll need to get your fingerprints so we can run them through our files."

     The Doctor grinned smugly. "If you think it'll help."

SCENEBREAK

     A few hours later, Castle came back to the desk from grabbing coffee to find Beckett hanging up the phone. She looked up and gave a grateful smile as she accepted the coffee. "That was Ryan. They found Karrow's keys swept under a car near where the body was found, and his car wasn't too far away."

     She turned back to her computer screen. "In the meantime, I found out Karrow's got a wife who died of a stroke a few years back, three sons, and a daughter. After we interview Smith I want to run down to talk to them. I also found out Karrow works for a bookstore called The Secret Garden off of 51st. Ryan's checking it out now."

     Castle sat comfortably in his chair across from Beckett's desk. "So, if this Doctor is involved with Karrow's murder, why would he try to break back into the crime scene?"

     "Maybe there was evidence on the body that he wanted to remove?"

     "Yeah, but Lanie said the body had been there for over eight hours." Castle pointed out. "He couldn't have removed any evidence before then?"

     Beckett shot Castle a look that was half irritation, half amusement. "You just don't want him to be the killer because he's got a cool toy and he talks about time travel."

     Castle abandoned pretense and let himself grin eagerly. "Oh, come on. First the body got sliced by a lightsaber, then the guy starts finding that Tyron energy thing, and he's dressed like some college professor. It's so obvious! He's a time traveler!"

     His partner raised an eyebrow. "Right, so he came from the future to help solve a murder." Sarcasm dripped from her tone.

     The writer nodded. "He said the killer had to come from the future, so the Doctor must have followed him here by tracing that Tyron energy. It all makes sense!"

     "Yeah, except for the part where there's no such thing as Tyron energy," Beckett pointed out drily. "Face it Castke, he's just a delusional criminal who won't even give us a proper name."

     "And what makes you say he's a criminal?" Castle asked with a raised eyebrow.

     "He said in the car that he'd been arrested before, remember? Once his fingerprints are taken I'm going to run them through our files to see if I can get a match." She stood. "Smith's waiting in the interrogation room. Let's go see what he says."

     They were interrupted as a woman's voice called out, "Detective Beckett?" They both turned to see a woman with pale, frizzy hair approaching their desk. She was older than Beckett, somewhere in her forties, but she walked without the brisk professionalism of the other cops. No, Castle decided, it was more of a swagger built from confidence, fit more for a lawyer than a cop. She held up a wallet with a police badge for Beckett to see. "Detective Melody S. Cage, I'm here about the suspect you brought in earlier, a John Smith, might identify himself as a doctor?"

     Beckett raised an eyebrow in surprise. "You're interested in the Karrow murder?" There was a slight edge in her voice. "That's my case. Do you have something about our suspect we need to know?"

     The woman flashed an unfriendly smile. "Maybe. Let's just say I've run into him before." She smirked, as if there was a joke here no one else was understanding. "I'll need to talk to him alone. All right?" Not bothering to wait for an answer she turned and strode off towards the interrogation room.

     Beckett gaped at the retreating Detective. For a moment, both she and Castle were lost for words. _Did that actually just happen?_ Castle wondered gleefully. Finally she pushed up out of her chair and marched after the woman. "Detective Cage, I don't know how they run things at your precinct, but this is _my_ case." She moved to block Cage's way, her expression steely. "You can watch if you want, but I'm running this my way."

     Cage appraised the woman in front of her with a grin that almost seemed dangerous. She seemed to like what she saw, for her grin grew wider. "Oh, feisty this one," she commented in a voice like a purr. When Beckett didn't react, her tone grew more professional. "Listen honey, I've got an all-access pass." She flashed her badge again, but something on it must have changed. When Beckett read it again, she clenched her jaw unhappily, but moved out of her way. Cage chuckled. "Much obliged," she said with a little mock salute. She started to open the door, then turned back to Beckett. "Oh, by the way, this one's a bit mental. Delusions and the like. Seems to think he's a time traveler and that I'm his wife. Poor dear. Like he'd have a chance with me. I'm just going to play along a bit, don't mind me." With that, she slipped into the room.

     From his spot by the desk, Castle was fighting back a grin. Beckett looked positively livid that this woman had stolen her suspect. _Oh, this is going to be fun!_ Anyone who could get under Beckett's skin was alright in his book. The detective and her partner headed into the observation room to watch through the one-way glass, not bothering to look at his obvious glee as she muttered, "Shut it, Castle."

     Still trying not to grin, he replied, "Wasn't saying anything."

     In the interrogation room the suspect hadn't looked up as the Detective entered the room. He let out a patient sigh, looking down at his hands. "Here we go. Listen, I don't know what leads you're following, but..." He trailed off when he finally lifted his head and saw who had entered the room. His eyes widened in both recognition and surprise.

     Detective Cage ignored the surprised suspect and made her way to the table. If there had any professional bearing in her walk before, it was completely shed now. Cage was smirking brightly, her posture becoming more relaxed. She lowered herself into the chair across from him and leaned back with an air of complete ease, finally flashing him a smug grin. "Hello sweetie."

**Notes for the Chapter:**

> EDIT: Updated a few details to fit better with the rest of the story. 
> 
> Alright, so I'm still not quite sure how many chapters this thing's going to have, but I have most of the plot planned out. And yes, there will be more chapters, despite what the story description says, I'm having trouble changing that. If anything here is horribly inaccurate, please call me out on it. I'll keep working on my other fics too, don't worry.


	2. The Karrow Family

**Summary for the Chapter:**

> Castle and Beckett contact Karrow's family, and Lanie has surprising news.

     Castle watched as Detective Cage pulled out the leather wallet with her badge, only this time the paper was completely blank. "I'm guessing this fell out of the TARDIS when you crash-landed. I found it on top of the empire state building." Her voice was a mixture of smug pride and amusement.

     The Doctor leaned back with a childish pout. "I didn't crash," he insisted with a dignified sniff. "I made an improvised landing."

     Cage raised an eyebrow. "You should be more careful with the TARDIS," she scolded, though her eyes shone with amusement. "She doesn't exactly appreciate these crash landings."

     The Doctor's pout deepened. "I didn't crash."

     The detective just rolled her eyes and asked, "Where are Amy and Rory?"

     From behind the one-way mirror, Castle turned to Beckett. "Who?" His partner just shrugged, keeping her narrowed gaze focused on Detective Cage.

     The Doctor's cheerful expression faltered. A look of deep sadness stole over his face for a moment, before being replaced by a forced smile. "Oh they're fine, they're safe." His smile faded, his eyes glazing over. "They're gone," he admitted dully.

     Understanding flashed in the detective's eyes. "You just left them behind after the hotel," she realized aloud.

     "Well, not just. It's been a while."

     Cage chuckled. "Alright then. Shall we do diaries?" She reached into her bag and pulled out a tattered blue journal. She opened it carefully, skimming through the pages with respect for the book's age. "Let's see. Have we done Demon's Run yet Doctor nodded. "Yes. Have you done Lake Silencio?"

     Cage's hands paused for a second, her smile faltering. "Which time?" she asked with a failed attempt at flippancy. Then she smiled again. "Yes, I watched Lake Silencio, about a week ago."

     The Doctor's eyebrows rose in surprise. "Huh. It was around a week ago for me too. Looks like we're at the same place for once."

     Cage's smirk softened into the first genuine smile Castle had seen her use. "Well there's a rarity." She leaned forward with a suddenly serious demeanor. "So what were you doing at that crime scene? You think whoever did that was alien?"

     Castle's brow furrowed. "If you ask me," he remarked to Beckett, "she's doing a really good job at playing along." Beckett shushed him, her glare shifting between Cage and the Doctor.

     The Doctor pulled out his sonic screwdriver and showed it to the detective, who frowned at what she saw. "There were traces of tyron energy near the body," he informed her. "So, alien I'm not sure about. And I can't be sure it was the killer. But someone who was at that garage is either an alien or a time traveller."

     Cage frowned thoughtfully. "Tyron energy's harmless in itself, but it could be connected to any number of weapons. We need to find whoever's behind this." She rose, reaching across the table and pulling the Doctor to his feet. "C'mon, we've got an alien to catch." A playful smirk played on her lips. "Geronimo."

     She led the suspect out of the interrogation room with the authority back in her posture. Beckett hurried over to intercept. "And where exactly are you taking my suspect?" she demanded.

     Cage swept carelessly past the detective, tugging the Doctor along behind. "To my precinct. I'll be able to process him more thoroughly there, and there's a number of other cases he's been involved with that are being handled there." She threw the Doctor a smirk over her shoulder. "Besides, I like having him where I can see him." The suspect's ears went red, and he looked away quickly.

     Beckett opened her mouth to argue, but Cage just sighed patiently and flashed her badge again. With a clenched jaw Beckett let them pass. Cage smirked. "Thank you dear. I'll let you know if we can help with the case at all." With that, she led the Doctor out into the elevator, giving a little mocking wave as the doors closed behind them.

     For a moment, Castle and Beckett just stared after her in shock. Castle blinked a few times, not believing what he had just seen. That woman had just waltzed in, stolen their only suspect, a d waltzed out without so much as an explanation. A thousand thoughts crossed his head, but what he finally settled for was, "Did that strike you as a little odd?"

     Beckett's eyes had taken on that steely look; Castle knew she'd thrown herself into full-blown detective mode. Cool, calculating, utterly determined. She turned away abruptly and strode over to the murder board. "It's out of our hands, Castle." Methodically she added the new information about Karrow to the board. "Cage is way above my pay grade."

     "Yeah, and when has red tape ever stopped you?" Castle asked with a smirk.

     Beckett let herself smile briefly. "After we talk to Karrow's family, I'll give Cage a call." Castle smiled back. He knew Beckett would never let a suspect go if they were needed to bring justice for a victim.

\----------------------------------------------------------------------------------

     A boy of sixteen with his father's curly hair was there to greet them when the detective knocked on the Karrows' door, but a teenage girl's voice rose up from in the house. "John, what did I tell you about answering the door?" A girl about Alexis's age shooed her brother away from the door, glaring at the strangers distrustingly. There was a fierce, wary look in her eyes, like a cornered animal. Castle frowned as he took in the teenage's tense posture and guarded look. All of his fatherly instincts protested against that hunted look. Something was definitely wrong with this picture.

     The girl brushed her short brown hair out of her lightly freckled face, her strange gray eyes flicking from the detective to her partner. "What do you want?" There was a sharp edge to her voice.

     Beckett held up her badge. "Detective Kate Beckett, NYPD. Are you Tanya Karrow?" The girl nodded warily. "Can we come in?"

     Tanya narrowed her eyes. "Why?" she asked curtly.

     Beckett raised an eyebrow at the girl's strange behavior but didn't comment. "It's about your father," she explained gently.

     Tanya stiffened, her expression flashing from hope to fear to distrust with terrifying speed. "Is he okay?" she asked hoarsely.

     Beckett sighed. "I'm afraid not," she told the girl gently. "He was found murdered this morning. I'm sorry."

     Raw grief blazed in the girl's eyes, and she stepped back with a choked cry. For a moment she looked completely vulnerable. Then her shields went back up and those gray eyes turned to steel. "Right." Her voice had an authoritative edge now. "You can come in and ask whatever you want. Just leave my brothers alone, all right? I'll break it to them myself. I don't need some police morons screwing up the job." She opened the door fully and retreated into the house, leaving Castle and Beckett to follow.

     Tanya led them to a homey-looking living room. From Tanya's behavior, Castle had been expecting run-down and ramshackle, but it actually looked quite comfortable. A little small, but Karrow hadn't been a rich man after all, and it was charming for its size. Two sofas sat angled opposite a fireplace with a TV above. Tanya sat on one, gesturing for the partners to sit on the other. Gone was the fear from before. Now she was full-on defiance and glares. "What do you need to know?"

     Beckett switched from comforting mode to detective mode. "When did you last see your father?"

     "Yesterday morning," Tanya shot off. She crossed her arms in front of her chest. "He didn't come home before I went to bed last night, which was around ten, so I just assumed he was working late. He does that sometimes. This morning I got the boys ready for school and assumed that Dad had gotten an early start. Also not unusual. He and Mindy run that store on their own, so they often have to work weird hours to get everything done."

     "Do you know if there was anyone he was having problems with? Maybe someone at work?"

     The answer to this question often became huge influence on a case. It could provide new leads, but it also revealed a lot about the person being asked the question. If they gave the answer too quickly, it was probably a bluff. Too eagerly and they had their own problems with the person. Not answering at all too quickly meant they were evading.

     Tanya, however, gave a new response. Her steely look became one of raw hatred, her hands clenched so tightly on the sofa cushions that her knuckles went white. Then the moment passed, and she was emotionless. "No one at all," she answered flatly.

     Beckett and Castle shared a swift look before turning back to the girl. "Are you sure?" the detective probed. Something about this was definitely off.

     Tanya nodded, a strange glint in her eyes. As if she was hearing the punch line of a joke no one else knew. "Positive," she insisted. "Tim was a quiet guy. Mindy and us are about the extent of his social life. And I know he didn't have any problems with Mindy. It was probably just one of those random muggings, you know? Some street thugs who thought it was fun to take out a harmless librarian." That hatred blazed in her eyes again.

     Before the detective can reply, two young boys of about six came running in. They tugged at the older girl's shirt like impatient puppies. "Tanya, Tanya! Can we watch the TV now?" Two identical, innocent faces looked pleadingly up at her as the ginger, curly-haired twins bounced around their sister.

     Something in Tanya's face softened. "Not just now, you two." With ease she crouched down to their level, a hand on one boy's shoulder. For a moment she looked almost motherly. "Ron, take Erik upstairs and show him that spider you caught earlier. Alright? I'm just talking to the nice detective here. We'll be done soon." As she turned back to Castle and Beckett, her posture became rigid, as though trying to shield her brothers from the detective's view.

     "Actually, I think we're done here." Beckett got to her feet, Castle following suit. "Do you four have somewhere to stay?"

     Tanya stiffened, but after a moment she nodded. "Our Aunt Blanche'll take us in," she said firmly.

     The detective raised an eyebrow. "We don't have any records of an aunt."

     Tanya's gray eyes hardened. "Check again," she challenged. "Blanche Sheet, older sister of our mother Mary, age 50. You'll find her." She drew herself up to her full height. Somehow, with the two little boys behind her, the skinny teenage girl in a baggy sweatshirt managed to look intimidating. "Now if you could leave so I could talk to my brothers, I'd appreciate it. I'm sure you understand, _detective._ " Her tone was biting on the last word.

\----------------------------------------------------------------------------------

     On the drive back, Castle was the first to speak. "Alright, is it just me, or was she hiding something?" Sometimes it helped to state the obvious, if only to annoy Beckett.

     The detective shook her head grimly. "There's definitely something she's not telling us about her father being threatened. But we're not getting much more out of her right now. Let's just go where the evidence leads us, and if we have to talk to Tanya again, we'll have some facts to throw at her."

     Castle gave his partner a worried glance. "Do you really think she had something to do with her father's murder?" Tanya had been uncooperative, yes, but she was clearly protective of her brothers, and she was only seventeen. _Alexis's age,_ he thought sadly.

     Beckett sighed. "I don't know castle. I hope not." Then she straightened her back and the detective took over again. "But either way she's hiding something, and we have to find out what."

\----------------------------------------------------------------------------------

     Back at the precinct, Beckett snapped more pictures on the murder board. "Tanya Karrow, seventeen, John Karrow, fifteen, and Ron and Erik Karrow, six." The four pictures were filed under the "Family" section of the board; "Suspects" remained blank except for the mugshot of the mysterious Doctor. The timeline was still pretty scarce, but it was a start.

     Castle watched as his partner leaned against the desk, staring intently at the murder board. "Did you find those records on that Aunt Blanche?"

     Beckett's brow furrowed irritably. "Yes, just like Tanya said," she said in annoyance. She turned to her partner. "Castle, I looked through Karrow's entire family, and there definitely wasn't a sister-in-law there before."

     Castle shrugged. "Maybe something was wrong with the file," he suggested. Then he brightened, a grin spreading on his face. "Or..."

     Beckett rolled her eyes. "Or what?" she asked resignedly.

     " _Or_ that time traveling Doctor used futuristic technology to change the records!"

     His partner threw him a glare that couldn't entirely hide her amusement. "You're just not letting this time travel theory go, are you?"

     "Oh come on!" Castle hedged, "Lightsaber cut marks, guy with a sonic screwdriver thingy, and records mysteriously changing! It all fits!"

     Before Becket could retort, the phone on the desk let out an insistent ring. The detective picked it up. "Beckett." She listened for a few seconds, then nodded. "We'll be right there." She hung up, then grabbed her coat from the chair. "That was Lanie. She found something she needs us to see."

\----------------------------------------------------------------------------------

     "Thanks coming so quickly," Lanie said as she led the two into the lab.

      "It sounded pretty urgent," Beckett replied. "What's up?"

     Lanie swept right past Karrow's body, which was laid out on the dissection table with a cloth draped respectful over, and led them to a table where a microscope sat out. "Bear with me, alright, 'cause this is kinda freaky." There was unusual tension in Lanie's tone.

     Beckett nodded, sharing a worried look with Castle. "What is it?"

     Lanie leaned against the table with one hand and turned to face the detective. Slowly she explained, "So I took a few swabs of tissue off the burn marks around Karrow's throat to analyze. I thought maybe I could find a hint of whatever might have caused it."

     "Alright," Beckett said warily.

     "Well, I didn't find it, but what I did find was really weird. These tissue samples aren't human."

     Whatever Beckett had been expecting, that clearly wasn't it. The detective looked well and truly stunned. She gaped at Lanie a few seconds before regaining her voice. "What?" she asked weakly. Castle had let out an audible squeak at Lanie's words, and now he was listening with mounting excitement.

     "You heard me," Lanie replied.

     "But you said you took them off Karrow."

     The medical examiner nodded. "I did. Then I took another sample from elsewhere on the body, and another. They all came out the same; not human. It's not anything I recognize either. I don't know how it's possible, but I will say your vic here must have been into something pretty freaky. You can't just change your DNA like that."

     Castle, whose excitement was now at the boiling point, turned to Beckett and whispered excitedly, " _Not in this time period._ " And for once, his partner had no retort.

**Notes for the Chapter:**

> Again, I know nothing of science or DNA or any of that, so if I'm wrong, don't shoot me. But feel free to tell me. And I'm really starting to enjoy this fic. The mystery's more fun to write than I was expecting.


	3. Bigger on the Inside

**Summary for the Chapter:**

> Castle and Beckett search for the only man who can explain what Karrow is.

     Beckett stormed into the precinct and immediately began barking out orders. "Ryan, I need you to go through Karrow's financials with a fine-tooth comb. If he's got a dollar out of place I want to know about it. Espo, go through medical history. Everything and anything. Give me something I can work with."  
   
     The two detectives looked at her in surprise. "You think Karrow was into drugs?" Esposito asked.  
   
     "More like genetic experimentation," Castle informed him.  
   
     This only made the partners look more baffled, but Beckett just ordered, "Get to work." Her stony expression offered no argument.  
   
     Ryan and Esposito turned hurriedly to their computers. After a moment however, Ryan turned back to Beckett. "Oh, we just got back from talking to Mindy, Karrow's hired help at the book store. She said she hasn't seen Karrow since three days ago."  
   
     This got Beckett's attention. "Three days?" she asked sharply. When Ryan nodded she frowned worriedly. "Tanya said she'd seen him yesterday morning. So either he's been going somewhere other than work the last three days..."  
   
     "... or Tanya lied about seeing him," Castle finished. A pang of sadness hit him at the thought of Tanya being part of her father's murder, but so far all the evidence pointed at her.  
   
     Beckett frowned thoughtfully. "I'll need to contact that aunt. In the meantime, Ryan, I'll need you to talk to neighbors, teachers, someone. Tanya's involved somehow, but I need a motive. Espo, take over financials from him.”  
   
     As Ryan scurried off to do her bidding, Castle turned to his partner, concerned. Gently he asked, “Are you alright?” She was being unusually closed-off about something case-related.  
   
     Beckett was quiet for a few moments. “How is it possible, Castle?” she finally asked.  
   
     Castle knew better than to bring up wild theories right now. His partner needed him to be serious, so he shrugged and suggested, “There are scientific ways to change your DNA. We’re not facing something impossible here.”  
   
     “Yeah, but to change it enough to no longer register as human?” She turned to him, biting her lip. There was an unusual air of uncertainty around her. “I’ve never heard of anything that can do that, Castle,” she admitted in a soft, low voice.  
   
     The writer reached out his hand, which Beckett clasped gratefully. “We’ll find an explanation, Beckett. We always do. We’ve faced weirder before, and there’s always an explanation.” He smiled at her warmly until she finally returned it, a small, grateful smile.  
   
     They just stayed like that for a minute, taking comfort in each other, until Beckett finally pulled her hand back. “Right now, it looks like there’s only one person who can answer my questions, and I don’t care how much red tape I have to go through.” She snatched up her phone and punched in some numbers as Castle watched in bemusement. She listened for a few seconds before saying, “Detective Kate Beckett, badge number 0334, I’m calling about one of your detectives, a Melody Cage, and one of the suspects she brought in.”  
   
     A few more seconds passed, then Beckett’s expression froze, the color fading from her face. “Say that again,” she said slowly. The detective snatched up a pad and paper and scrambled to write something as she continued to listen to the other end. “What about a suspect, a John Smith?” A few more seconds, then she shook her head bitterly. “No, of course not. Thank you.”  
   
     She slammed the phone down with a curse. "Son of a bitch." The detective looked grimly up at her partner. "They don't have any record of a Detective Melody Cage. She's a fake, and she's got our suspect."  
   
     Castle wasted no time. He grabbed his coat and followed Beckett hurriedly towards the elevator. "So she used a fake badge?" he asked.  
   
     "Must have," Beckett said in a clipped tone as they stepped inside. "It was a good one too."  
   
     "So if they worked this hard to break out, that means they're mixed up in Karrow's murder somehow," Castle reasoned.  
   
     "We need to find out," Beckett agreed. "And I know just where to find them."  
   
SCENEBREAK  
   
     It was getting dark by the time they reached the scene of Karrow's murder. When they arrived at the parking garage, it was still closed off, but no one was around. Beckett frowned. "Where is everyone?"  
   
     Castle shrugged. "Out for a drink?"  
   
     Beckett rolled her eyes, then pulled out her phone. "Alright, I'm calling it in, we need to get a surveillance team in to wire up the area."  
   
     A familiar voice purred, “Well, that’s going to be a problem.”  
   
     Beckett and Castle whirled around to face Cage, only to find themselves at the barrel end of a very strange gun. Cage was grinning at them with a mixture of cockiness and ferocity. The mock politeness from before was gone. Now her smile was two steps away from feral. “Well now, this is a fun turn-up,” she remarked calmly, a tone at odds with the gun she was pointing at them. “I wasn’t expecting to see you two again.”  
   
     Castle shared a quick glance with Beckett before asking, “Where’s Smith?”  
   
     “Oh, he’s out shopping, the dear,” Cage said with a smirk. “Don’t think you’ll be around long enough to see him.”  
   
     Beckett hand inched towards her holster, but Cage switched the gun to focus on her. “No, let’s keep your gun out of this, shall we, I’d hate for things to get messy. Oh, and be a dear and drop the phone.”  
   
     The detective put up her hands, letting her cell phone land with a clatter. “Then why don’t you just put your gun down and come with me?” She asked wryly.  
   
     Cage laughed, a cold, biting chuckle. “Oh, but where’s the fun in that?” she asked, voice smooth as a purr. The laughter died from her eyes and her tone became noticeably serious. “Listen you two, you’re not equipped to get mixed up in all this. So why don’t you two just pop off to your little precinct and forget about this case, hmm?”  
   
     Castle raised an eyebrow. “Are you trying to scare us off the case?”  
   
     “Yes.” Cage said simply. There was something more sincere in her tone now, almost sad. “This case is way over the heads of the NYPD. We don’t need cops screwing up the job.”  
   
     Beckett stiffened. “I don’t let cases go,” she warned in a low voice. She took a few slow steps towards Cage, which the gun-holder strangely allowed. “I’m giving you this one warning, Cage. You’re not scaring me off this case. I’m here for the victim’s family. To get justice for someone who was murdered. I don’t back down. I don’t let cases grow cold. And I don’t scare easily. So if we leave here today, don’t think you’ve won, because I’ll keep coming after this case until it’s solved. Understood?”  
   
     Cage looked over Beckett like she had at the precinct, only now there was nothing condescending in her gaze. There was respect, and admiration, and even sympathy. “You could die,” she warned.  
   
     Beckett paused, her gaze drawn to Cage’s gun. “Is that a threat?” she asked coolly.  
   
     “No, it’s a warning.” She looked from Castle to Beckett with a knowing gleam. “I’ve seen things you two wouldn’t believe. I’ve faced dangers far beyond your wildest dreams.” She took a shaky breath. “And I have seen so many good people die in the name of stopping the bad. From what I hear, you two are good at your job. Your city needs you. Don’t put yourself in the line of fire for this one. Please.”  
   
     Castle felt a chill at her words. He and Beckett shared a quizzical glance. Cage’s words called to mind gangs, the mafia, grand conspiracies, but somehow none of these explanations seemed grand enough for all Cage was implying. Something else was going on here, far beyond one murder, but what it could be Castle didn’t know.  
   
     After looking at Castle for confirmation, Beckett turned to Cage and told her, “I don’t care what you’re mixed up in. I will do what I have to to bring closure to Karrow’s family.”  
   
     Sadness flashed in Cage’s eyes. She opened her mouth to reply, but a new noise interrupted her. It was a strange, almost extraterrestrial sound, a reverberating _vworpp, vworpp, vworpp_. Something seemed to shimmer in front of them, but after a moment it was gone. Then it came back, and faded, and grew clearer, and faded again. Each time it grew clearer, and each time Castle wondered just what he’d been dosed with. He was hallucinating, right? There definitely wasn’t a blue police box from the 50’s materializing in front of him with a cheerful _vworpp, vworpp_.  
   
     Finally, it became totally solid, and the noise stopped. Beckett gaped incredulously at the box, blinking repeatedly, but Cage just looked annoyed. “That man and his sense of timing,” she grumbled.  
   
     Beckett seemed to finally regain her command of speech. “What man?” she whispered, wide eyes still focused on the police box. She seemed to have quite forgotten about the gun Cage was pointing at her. Castle gave it a wary glance, but Cage just rolled her eyes and put in away in her holster.  
   
     Cage nodded towards the box. “That man,” she said simply.  
   
     As if things couldn’t get any weirder, the door to the police box opened, and the suspect from earlier poked his head out. “See, I am perfectly capable of… oh.” He trailed off as he noticed Castle and Beckett. Unlike Cage, however, his gaze was not hostile, merely curious.  
   
     Cage just rolled her eyes. “Honey, what did I tell you about parking the car when we have guests?”

     “How was I supposed to know we had guests?” The Doctor protested.

     Cage raised an eyebrow. “You could have used the life form scanners.”

     “It doesn't have life form scanners,” the man said with a sudden scowl in her direction.

     She gave an amused smirk. “The red dials by the screen.”

     The Doctor glanced back inside his box for a moment before turning to Cage with a pout. “I thought they were for decoration,” he stated lamely.

     Cage let out a sigh. “Honestly, you're hopeless. I don't know why she puts up with you.” There was an easy familiarity in their banter. The writer in Castle could sense a good many shared stories between the two of them.

     The rest of Castle was trying to put the pieces of his brain back together as he gaped idiotically at the blue police box. “What... how did that happen?” He finally asked. Shock was slowly giving way to excitement. This was real. There was an actual disapearing police box. There were so many words the writer could think of to describe the situation, but the one he finally settled on was _awesome._

     The Doctor's expression sobered as he looked from Castle to Beckett. He stepped slowly out of the police box, his eyes taking on a mournful look. “Look at you two,” he said softly. “You two together, facing off the world, ready to face the darkness 'cauuse you don't know what's really there.” He let out a painful breath. “So like Amy and Rory.” He threw Cage an uncertain glance.

     Her expression grew warm and sympathetic. “Amy and Rory chose to travel with you, dear. Remember that. It was their choice. And they're fine! They're safe and sound with their own place.”

     The Doctor sighed. “No thanks to me.”

     Cage narrowed her eyes. “Don't blame yourself, okay? Not everything that goes wrong in the universe is your fault.” She nodded towards Castle and Beckett. “These two work with the police, Doctor. They can handle it. Tell them.”

     The Doctor looked from Castle to Beckett, his eyes looking far older than they had a right to be. Then he brightened, the solemn mood slippig away with alarming ease. “Oh, what the hell, I love a good introduction.”

     He grinned brightly at Castle and Beckett. “Hello! I'm the Doctor. I'm an alien from another world, and this,” he paused, snapped his fingers, and the doors of the police box opened inward, “Is my TARDIS.”

     Castle and Beckett stared in wonder and shock at the box before them. Without a word they each held out a hand for the other, grasping hands tightly. Still holding hands, they stepped mutely into the police box.

     If there was shock before, that was nothing compared to what was felt now. The inside of the police box was completely massive. A wide dome roof overlooked what looked like a futuristic console room, only more homey in colors. Castle backed up a bit so he was outside. The box was scarcely large enough to hold three people. Back inside. He blinked. Massive.

     Shock subsided to wonder. Castle grinned gleefully, childlike excitement bubbling up inside him. He turned to his partner, only to see her looking around with a mix of fear and hope. She looked fearfully at Castle. “Is this real?” She asked quietly. Her hand grasped his tightly. Castle realized that she was trusting him with confirmation of this fantastic sight. She trusted him to tell her what was dream and what was real. To tell her she wasn't going insane. Warmth flooded his chest as he realized just how much she trusted him.

     He gave her hand a tight squeeze. “It's real. I see it too.” The fear faded from Beckett's eyes. They shared a smile of wonder and excitement before turning back to stare at the console room once more.

     There was silence for a few moments as they took in the sight of it. After a while, Castle became concious of Beckett still holding his hand in that tight grip. She was still trying to take it all in, he realized. The serious atemosphere was becoming uncomfortable, so he turned to Beckett with the most childish grin he could muster. “ _It's bigger on the inside!_ ” he gushed with excitement.

     The serious atmosphere was broken. Beckett cracked a grin, her grip on his hand loosening slightly. “Yeah, I got that Castle.”

     “Oh, I love that bit.” Castle and Beckett whirled around to see the Doctor and Cage standing behind them. The Doctor was grinning brilliantly, a knowing gleam in his eyes. “Every time, it gets better, but I just love the 'bigger on the inside' bit. It's just classic.”

     Beckett's grin faded at the sight of the Doctor, to be replaced by the cool professionalism of a detective. “Who are you? Why are you interested in Karrow's murder?”

     The Doctor folded his hands behind his back and bounced up on his toes before going back on his heels. “I'm the Doctor.”

     Beckett narrowed her eyes. “Just the Doctor?” She asked, drawing back from the conversation on the way to the precinct.

     He nodded, amusement gleaming in his eyes. “Just the Doctor,” he confirmed. “I'm a time traveler and an alien, but I've always had a thing for Earth. It's fascinating really, how often you lot manage to make yourselves the target of alien invasions and take-over-the-world schmes.”

     “So is this your time machine?” Castle asked. His gaze was darting all around the console room, trying to take in everything he possibly could.

     “Yes!” The Doctor bounced excitedly over to the console and began fiddling with some knobs and buttons. “The TARDIS, stands for 'Time and Relative Dimmensions in Space.' She can travel anywhere in time and space.” He turned to Cage. “River, could you hold down that switch for me?”

     Castle's brow furrowed. “Who's River?”

     Cage laughed, real, warm laughter, not the cold chuckle from before. “I am.” She held out a hand for Beckett, who shook it bemusedly. “Doctor River Song, Archaelogist. Sorry for the confusion, I just couldn't leave this idiot rotting in a cell in New York. Worlds to save and all that.”

     Castle raised an eyebrow as River turned to him with an outstretched hand. As he shook it he asked, “Where did you get Melody S. Cage from? I mean John Smith I get, but Melody Cage?”

     The Doctor looked up in surprise. “Melody Cage? Why not just use Melody Pond?”

     River smirked. “Melody Pond is my birth name, which I changed after... certain events,” she explained to Castle and Beckett as she made her way to the switch the Doctor had indicated. “But that name has a few records to go with it, as does Melody Rogers. So I went with S. Cage.” She turned to the Doctor with a smirk. “S. for Storm.”

     The Doctor chuckled. “Stormcage. You named yourself after Stormcage?” He asked with amusement.

     River shrugged easily. “Well, I was breaking someone out of a prison, so I figured it fit,” she said breezily.

     Beckett turned to the Doctor. “What's Stormcage?” She asked.

     He smirked at River briefly before turning back to Beckett. “A prison in the 51st century. But we're getting off the point.”

     The Doctor pulled the screen around so they could all see it. There were a lot of strange circular designs, but in the center were what looked like line graphs. Beckett looked at it with eyes narrowed in concentration. “What is it?”

     The Doctor rocked back on his heels, brow furrowed. “It's analyzing the traces of tyron energy that I was trying to look at before. I needed the TARDIS to try to trace the source.” At the partners' confused look he explained, “I was traveling nearby when the TARDIS first picked up the traces of tyron energy. I tried to follow it, but I might have been a mite off with my calculations.”

     “He means he crashed,” River spoke up from the other side of the console. “Honestly, you should see how he flies her, always racing about throwing up random switches and banging the console with a mallet. I'm surprised he doesn't crash more often.”

     Castle turned to the Doctor. “I remember you mentioned tyron energy before. What exactly is that?”

     “Tyron energy can be used to preserve a great deal of heat,” the Doctor explained at rapid-fire pace. “The energy manipulates the heat and puts it on a loop so that every time it starts to die out it replenishes itself from the last spark of energy. Thing is, no one's supposed to discover tyron energy for another couple hundred years.”

     Beckett looked up sharply. “Could this energy keep something like metal hot enough to burn without melting it?”

     The Doctor nodded. “Easy. It would cover the metal like a second skin. Well, not like that at all. Well, sort of. Think of that if it helps.” He frowned. “Why?”

     Castle explained, “Karrow was killed by a blade that burned his thoat.”

     The Doctor grinned. “Oh, that is brilliant! Someone zapped in from the future to murder someone from the past with a blade heated by tyron energy. The question is, why?"

     Castle and Beckett shared a glance. The writer asked, "Would it help if Karrow wasn't human?"

     The Doctor looked at him in surprise, pausing from his manic dabbling with the console. "Why?"

     "Our medical examiner says that Karrow's DNA isn't human," Beckett admitted reluctantly. Castle could see she was still coming to terms with that particular bit of information.

     River spoke up again. "Maybe it was some sort of hit? Someone sent to take out alien refugees masquerading as human?"

     The Doctor looked thoughtful. "Could be." After a few moments, he turned to Beckett with a sudden grin. "Did you tell anyone that River wasn't actually a cop.

     Beckett frowned. "No. Why?"

     "Because I need to analyze that body," the Doctor explained, an excited grin on his face. "And you and River are going to get me in."

**Notes for the Chapter:**

> I'm just churning these out, aren't I? I'm unusually motivated at the moment, so I'm rolling with it. Besides, it's easier to keep the characters consistent if I just right straight through. Enjoy, and expect more soon.
> 
> And sorry if Eleven's acting a bit Ten-ish at the end there, my writing got a bit off there.


	4. Broken

**Summary for the Chapter:**

> River and the Doctor stay at Castle's place overnight.

*Yes, in this chapter, Beckett is staying at Castle’s place like in Significant Others. But it’s not set during that episode. So she’s staying at Castle’s place because of renovations being done to her building and because I said so. Also narrative convenience.*  
   
     The Doctor didn't take too well to the idea of stopping for the night. "But there's still stuff to do," he whined when Beckett brought it up.  
   
     The detective raised an eyebrow at his childish behavior. "And making ourselves too tired to properly work on the case won't help anything. Besides, the morgue'll be closed, we won't be able to access the body anyway." The Doctor opened his mouth to reply, but Beckett cut him off with, "And no, we're not breaking into the NYPD's morgue in the dead of night. We'll get some sleep and keep working tomorrow."  
   
     Castle looked from River to the Doctor. "Do you guys have a place to stay?"  
   
     The Doctor looked surprised for a moment, then grinned cheerfully. "Of course. We've got the TARDIS."  
   
     Castle gave the police box a critical glance. "Oh yes, staying in a box in the middle of a creepy empty parking lot. Sounds fun." Then he brightened. "You should come back to my place. I've got a couple extra rooms, and we'll have dinner."  
   
     The Doctor’s smile faded. “Oh no, I really couldn’t. I don’t do… dinners and things.”  
   
     Beckett narrowed her eyes, crossing her arms. “I’m still not convinced you two aren’t mixed up in this somehow. So you can either spend the night in a cell, or come to Castle’s place with us so I can at least keep an eye on you.” She fixed him with that Beckett glare that sent criminals running.  
   
     The Doctor continued to hesitate, but River just rolled her eyes. “Oh, ignore this idiot. Dinner would be lovely, and we’ll be glad to stay the night.” She swept right past the pouting Doctor and started off towards the car. “Come along, Doctor.” Castle could practically hear the smirk in her tone.  
   
     The alien shook his head. “Oh, fine. Fine fine fine. But I’m not leaving the TARDIS here, I’ll just pop over and park her at your house.”  
   
     Castle looked eagerly at the box. “So you’re going to fly it there?”  
   
     “No, not fly her. She can disappear here reappear there,” the Doctor explained as he strode towards the TARDIS.  
   
     The writer followed him like an eager puppy. “Can I come?”  
   
     The Doctor gave him a surprised glance, then grinned. “Well of course you’re coming, how else am I going to explain popping up in the middle of your living room? Oh, and where is that incidentally? I need an address.”  
   
     Castle gave it to him as they stepped back into the TARDIS.  The grand interior still brought an idiotic grin to his face. The Doctor hurried here and there around the console, throwing up switches and pushing buttons. He looked over at Castle. “I don’t think I got your name by the way. Didn’t your partner call you Castle? Nice name Castle, almost as good as Pond.”  
   
     The writer tore his gaze away from the amazing interior to look at the Doctor. “I’m Richard Castle, and my partner’s Detective Kate Beckett.”  
   
     The Doctor paused from his work with the console. He looked up at the writer with wide eyes, surprise evident on his face. Castle couldn’t help feeling smug. He guessed that it took a lot to surprise the Doctor and felt accomplished he had managed it, though he didn’t know how. “No. You’re Richard Castle? The writer?” When Castle nodded, a huge grin broke out over the alien’s face. “Oh, this is fantastic, I always wanted to meet you. In fact I remember I meant to take Amy and Rory to meet you, but then we ended up in the ice age and things got a little complicated. I got arrested by Richard Castle!”  
   
     His gleeful babbling mostly bemused Castle, but he felt unusually touched by the revelation of this particular fan. “You said you’re from the future, right?” he asked slowly.  
   
     The Doctor nodded, still grinning. Then understand flooded his face. “Oh, of course, you’re wondering if…” He shook his head with a chuckle. “Don’t worry. Your books last for a long, long time. I mean, you’re no JK Rowling or Charles Dickens, no offense, but your Heat series is considered far and wide one of the most realistic, heartfully portrayed detective series of the era. They say the romance between Heat and Rook is the most realistic aspect.” His eyes widened in surprise. “Wait a minute, Kate Beckett. Of course! The inspiration for Nikki Heat! Oh, that is brilliant! I was arrested by the inspirations for Nikki Heat and Jameson Rook!” With a delighted laugh he returned to his work with the console, dashing around to throw up more switches.  
   
     Castle watched silently, thinking about what the Doctor had told him. He had never been overly concerned with how his books would last. They were meant very much for the here and now. He had never written them to be classics like Lord of the Rings or Sherlock Holmes. But knowing that he was remembered, that his books were remembered, even after he was gone… And that the books remembered were his Heat books only made it better. He had put so much of his and Beckett’s relationship into that book. It was almost like it was them who would be remembered for all that time to come. Castle smiled to himself, letting himself be warmed by the thought. He had preserved the thought of Kate Beckett for years and years to come.  
   
     “Although, I have always wanted to ask, why did you kill Derrick Storm?”  
   
     The serious moment was broken as Castle held back a chuckle. “To tell the truth, he was getting boring to write.” He approached the console, looking at the Doctor’s work. “So we’re just going to appear in the middle of my living room? Won’t the big blue box raise a few questions?”  
   
     “No no no, I’m setting it on invisible.” The Doctor frowned for a moment. “Not a fun setting, but it gets the job done. Oh, and we’re on silent too.” With a grin in Castle’s direction, he pushed forward a final lever.  
   
     The TARDIS gave a massive shudder, almost sending Castle to the ground. He clutched at the console desperately as the TARDIS continued to shake. The writer turned to the Doctor, who was grinning maniacally. “Can’t this thing fly any smoother?”  
   
     The Doctor just shook his head. “Where’s the fun in that?” he laughed.  
   
     Castle could come up with several ways to disagree, but never got the chance. With a final violent shudder the TARDIS finally stilled.  
   
     As Castle struggled to get used to the sudden change in balance, the Doctor dashed over to the door, throwing it open and grinning out at what he saw. “Very lovely place. Not better than my TARDIS though.”  
   
     The writer finally made his way to the door, pushing past the Doctor, and found himself in the middle of his living room. He looked back at the now-invisible TARDIS, which moments ago had been in an abandoned parking lot, and laughed incredulously. “It actually appeared here! It’s a real spaceship!”  
   
     The Doctor followed him out of the TARDIS, closing the door behind him. “Of course it’s a real spaceship!” He tried to sound offended, but he too was grinning. “We’ll just leave it here for now. I just have to remember where I parked it.” His look faded to one of confused remembrance. “It’s never good to lose an invisible TARDIS.”  
   
     Castle was about to ask what had happened last time that happened when footsteps sounded from upstairs. The Doctor hastily locked the TARDIS as a red-haired woman descended from the stairs. She gave a slight jump when she saw Castle and the Doctor. “Oh! Oh, hello darling, I didn’t hear you come in.” She looked curiously at the alien beside him. “And who is this?”  
   
     The writer turned to the Doctor. “Doctor, this is my mother Martha Rogers. Mother, this is the Doctor. He’s from out of town and has agreed to help consult on the case, and he didn’t have anywhere to stay so I offered a room.”  
   
     Martha raised an eyebrow.” Well, how generous of you.” She turned to the Doctor with a gracious smile. “It’s good to meet you, Doctor…?”  
   
     The Doctor shook her offered hand with a grin. “Just ‘the Doctor.’” He explained cheerfully. “I had a friend named Martha once, brilliant she was, absolutely brilliant.”  
   
     Martha ignored the strange comment at the end, focusing instead on the first part of the Doctor’s introduction. “Oh. Are you an actor then, Doctor?”  
   
     It was the second time the Doctor had managed to look surprised. “No. Why?”  
   
     “I’m an actress, and I thought maybe the Doctor was your stage name,” she explained. “I’ve met many an actor who built a new name for himself when taking to the stage. Of course, I was always happy with Martha Rogers, but my son here decided the name Rogers didn’t hold enough grandeur for him.” She sent her son a brief, mock glare, but he just grinned back. “Are you a writer then?”

     The Doctor shook his head, gaze darting around the living room with child-like curiousity. “No, I’m traveling mostly. I have some information that could help the NYPD with their case.”

     "Oh?" She looked at Castle questioningly, but when no more information was forthcoming, she turned back to the Doctor. "Well, you are most certainly welcome to stay here tonight."

     A brisk knock sounded from the front door. "Ah, that'll be Beckett I suppose," Martha commented as Castle hurried to the door, opening it with a welcoming grin.

     The detective in question stepped in, followed by River, who looked around the flat with interest. Beckett slipped her coat off and hung it up. "Hey Martha."

     "Hello again, Detective Beckett," the actress greeted warmly.

     River stepped up to the actress, holding out a hand. "Doctor River Song, archaeologist. I'm the Doctor's partner."" She shot the alien in question a smirk.

     Martha shook her hand graciously. "Its very nice to meet you Doctor Song, and you and your partner are welcome to stay the night." She headed over to the closet to grab her coat.  "Well, I would love to stay and mingle, but I have other obligations this evening. My acting school is hosting an event this evening and I've volunteered to help. Have fun, you four." With that she swept out the front door, leaving the two doctors alone with the writer and the detective.

     There were a few moments of awkward silence. The Doctor was still gazing around the flat curiously, while Beckett seemed lost for words now that she was faced with a time traveling alien. The silence stretched on for a few more moments, until Castle couldn't take it anymore. "So, who wants dinner?"

SCENEBREAK

     Dinner helped to ease the tension. River luckily had better social skills than her companion, so she soon had the four engaged in comfortable conversation. The archeologist was telling them a story that had Castle in hysterics and even had Beckett laughing, though she remained skeptical of any mention of aliens. "... so there we were running from the locals, with only one shoe between us, when Rory twisted his ankle. The Doctor literally had to carry him bridal style. Oh, we were ready to kill him."

     Castle was crying he was laughing so hard. "And all because he ate a banana?" he asked when he got his breath back.

     The Doctor was half scowling, half laughing. "I like bananas!" he protested half-heatedly. "And it was just sitting there! How was I supposed to know it was the ancestral fruit?!"

     River rolled her eyes. "Oh, I don't know, maybe crack open a history book sometime _before_ visiting a new place?"

     The Doctor scoffed. "Who needs history books? Conjecture and guesswork. I don't travel through time and space so I can read it all happening in some stuffy old textbook."

     River just shook her head and turned to Castle and Beckett. "You see what I have to put up with?"

     Castle noticed the warmth in her eyes even as she said this, and the way the Doctor looked at her when she wasn't looking. River's obvious flirting from earlier had made him suspect something might be between them, but now, with their simple familiarity and shared glances, there was no doubt in his mind. He didn't know all the variables of their story, but he could see enough to tell it was a love story.

     And that there was something tragic burrowed underneath.

SCENEBREAK

     After dinner, River asked to be shown her room, explaining that she'd been kept up two days trying to find the Doctor again and could really use the rest. Castle lent her Alexis's room and excused herself for the night. Castle and Beckett started clearing up the dishes from dinner. The Doctor offered to stay out on the couch since he didn't plan on sleeping anyway, which earned a raised eyebrow from Beckett. "I don't need you exhausted for the case tomorrow. Get some sleep, okay?"

     The alien pouted, an expression Castle was becoming increasingly familiar with. "Time Lords don't need sleep," he grumbled.

     Beckett paused, expression questioning. "Time Lord?" she echoed dubiously.

     The Doctor didn't seemed fazed by her tone. "Yeah. Time Lord. That's what I am."

     "Your species is called _Time Lord_?"

     The Doctor nodded, clueless to her incredulous expression. "Yeah."

     Beckett threw Castle a look that clearly asked _Is this guy for real?_ Castle shrugged, but he couldn't keep the smile off his face. If Beckett was being snarky about a name, she was clearly getting over the earlier shock of the TARDIS. The detective turned back to the Doctor as she set the last of the dishes in the sink. "So are there other Time Lords around here pretending to be human or something?"

     The Doctor stiffened, a look of pain flashing in his eyes. Castle frowned. The expression was a familiar one, but not on the Doctor's face. It was how Beckett looked whenever someone brought up her mother. Several possible stories popped up in the author's head, but he waited for the Doctor to answer rather than say anything.

     The Doctor gave a weak attempt at a smile. "No, we had our own planet, and our own time machines. We didn't need Earth. In fact, most of them thought I was daft for liking you strange humans."

     He soon busied himself with playing with his sonic screwdriver, but Beckett had clearly caught onto his tone. "You _had_ your own planet?" she questioned gently. Castle recognized her tone as the one she used when she was trying to get emotional suspects to talk.

     The Doctor was silent for several moments, morosely fiddling with the screwdriver. Castle and Beckett settled easily into the usual instincts of interrogation and let him keep the silence as long as he needed. When he spoke again, his voice was dull, as though trying to keep the words from hurting. "My planet, Gallifrey, it burned." Another pause. "There was a war. The last great Time War, between my people and a race called the Daleks. We... lost. Everybody lost." There was no bitterness, no raw grief. Just a voice that sounded dead and eyes that were far, far too old.

     Castle waited for a few moments before gently prodding, "But you're still here." He was careful not to seem accusing or too pushy. It was an old routine, one perfected through sheer use. He and Beckett had interrogated so many suspects at this point that they knew just the right phrase to make someone talk. Even their posture had changed; their hands were still busy, so as not to seem too pushy or needing of the information, but turned slightly towards the Doctor so as to give him their attention. Aliens and time travel were beyond their general expertise. But getting someone to talk? That was their job.

     The Doctor laughed bitterly. "Oh yes, I survived. The only one." He looked up with something of a wild despair in his eyes. "The very last of the Time Lords. How do you like that? And now I can't even keep my companions safe. One by one I've failed them, lost them."

     He didn't know what the Doctor meant by "companions," but he could see the Time Lord was breaking down in front of them. Time to switch tactics.

     Beckett took a confident step towards the Time Lord, her voice low and soothing. "I'm sorry," was all she said. It wasn't the meaningless apology of someone who didn't know what else to say. It was the reassurance of someone who's shared a deep pain.

     Sanity crept back into the Doctor's eyes. He have Beckett a thoughtful look. "You lost your mother." It wasn't a question. _He must have read it from my books,_ Castle reasoned.

     Beckett nodded. "She was murdered when I was nineteen," she explained in that same calm voice. Only Castle could see the turmoil she was hiding. "I'm not saying that's anything to losing your entire planet. I can't imagine what that must have been like. But I can understand missing somebody do bad it hurts, of trying to do something, anything to fill the hole they left."

     The Doctor didn't say anything, just looked thoughtfully at Beckett for a few moments. Then he smiled slightly. "Castle was right. Kate Beckett, you are extraordinary." The detective fumbled a little under the praise, but the Doctor didn't seem to notice. He turned, suddenly the energetic child once more. "Well, off you two pop, you've got sleeping and whatever it is you humans do to do." He headed off to the couch, flopping down onto it without another word.

     Castle and Beckett shared a worried look. This was a side of the Doctor they hadn't seen before. He was smiling again, but now they knew that was just a mask. They had seen the real pain that lay underneath, just a glimpse of it, and they had seen that the Doctor hung to sanity by threads.

     And yet oddly enough, Castle could see that this had made Beckett trust him more, not less. She'd stopped trying to deny he was an alien, and the look on her face as she watched him leave was one of grim understanding. This man wasn't a liar. He was broken, and that, finally, was something Beckett could understand.

     Without a word they headed off to bed. They had a long day ahead of them tomorrow.

**Notes for the Chapter:**

> This is the chapter where I discovered that Martha, the Doctor, and Beckett are hard to write, the former any time, the latter two when they're having a deep moment. This is also not the chapter where we find out what's going on with the Karrows, sorry to anyone I told that, that will be next chapter. For now, enjoy some character bonding.
> 
> For the record, I know the Doctor doesn't do family dinners. He never does family dinners except when it's Rose or the Ponds. I know that, and I'm not trying to undermine that by saying Castle and Beckett are immediately that important to him. But those dinners offered to him are a means of thanks after he's saved that world, and he feels he can never accept that. That's not what this dinner is. He hasn't saved the world yet, they're not thanking him for anything. They're trying to keep the team together in the middle of saving the world, and he can see the sense in that. Also, River wanted to, and since she just went through Lake Silencio again the Doctor has no will to say no to her.
> 
> I've been staying in Castle's POV this whole time, which was not my original intention. I don't even want to think about tackling the Doctor's POV, but I think I'll try to add some Beckett and River later.
> 
> And yes, I resurrected the Derrick Storm joke. Because I could.


	5. Breaking Illusions

**Summary for the Chapter:**

> The Doctor examines Karrow and truths are uncovered.

     The next morning woke Beckett bright and early. She wanted to have a good start on the case. The detective dressed quickly and made her way out into the kitchen. 

     Castle and the Doctor were already up and eating breakfast. The Doctor was chatting animatedly with Castle, waving his hands excitedly in an effort to explain something. Castle looked completely entranced, that adorable idiot grin on his face. The sight of it brought a smile to Beckett's own lips. Castle had changed and matured in so many ways since he'd been the callous playboy she met, but he would always have this wonderful inner child to him. It was one of the things the detective loved about him. There was just something about him that let him see the world as something to be constantly excited about.

     At first, she'd thought the Doctor was very much the same. He'd acted a lot like Castle after all, always the goofball, always the one with a quick joke. But the child in him wasn't built from joy; it was built from fear, fear of something inside himself. The world wasn't exciting to him, not innocent; it was more like he forced himself to look at it that way. Like if he stopped being excited about life, stopped smiling for even a moment, he would simply fall apart.

     Beckett had only known the guy for a few days, but she felt like she knew him, or at least understood him, better than that time would usually allow. They shared that pain of loss and guilt.

     Shaking herself out of her thoughts, Beckett strode into the kitchen and grabbed a banana from one of the cabinets. "I'm heading to the precinct," she informed the two.

     Castle looked surprised. "Already? Aren't you going to get breakfast first?"

     In response Beckett held up the banana, which Castle eyed critically. She laughed at his dubious expression. "I'll grab something on the way there," she assured him. "I just want to get there early so I can call 'Detective Cage' and give her plenty of time to get there." She threw the Doctor a quick, searching glance, still vaguely hoping to see a hint of deception. There a tiny voice in her head whispering that maybe, _maybe_ it was still all some kind of set-up. But she knew it wasn't. It was all real, and now that the shock had worn down she was starting to accept that.

     The Doctor looked up eagerly. "So there's not any problems with getting me in to see Karrow?"

     Beckett nodded. “I’ll tell them that the charges were dropped against you as long as you agreed to help, and that you’re working with Detective Cage.” Her eyes narrowed into a sudden glare. “Listen, I’m only doing this because you say you can help solve Karrow’s murder, so just do as I say and keep your mouth shut unless you have something valuable to contribute.”

     Amusement glittered in the Time Lord’s eyes. “I won’t say a thing,” he promised. Beckett groaned when she recognized the tone in his voice. It was the same tone in Castle’s voice whenever he promised to stay in the car.

     She gave Castle a quick glare. “Are you sure you two aren’t related?” She asked drily. Far from looking insulted, Castle seemed absolutely delighted at the thought. Shaking her head at her partner’s antics, the detective slipped out of the apartment and started off for the elevator.

SCENEBREAK

     When she reached the precinct, Esposito and Ryan were waiting with news. “I went over Karrow’s financials,” Esposito informed her as she sat at her desk. “Nothing unusual there. _But_ , then I did a scan of his medical records.”

     Beckett tried not to look too nervous. “What did you find?” She hoped her partners wouldn’t realize she knew more than she should.

     “Nothing.” Beckett blinked in surprise. “Absolutely nothing. No surgeries, no check-ups, not so much as an aspirin bought in his entire life. I called up that sister-in-law, and she said the man hated doctors with a passion. Apparently he was into all kinds of herbal remedies and such.”

     Beckett leaned back in her chair. “There were a lot of plants in their house,” she recalled. In truth, it didn’t surprise her. If Karrow really was an alien, it made sense that he wouldn’t want to go anywhere near a doctor.

     Ryan spoke up. “I talked to the Karrows’ neighbors, and they said the family’s pretty quiet. Always keeping to themselves, not a lot of visitors. No one ever saw Karrow leaving at weird hours though, so I don’t exactly see him being a drug dealer. No one I talked to saw any arguments between Tanya and Karrow, but they said they wouldn’t have known anyway since Karrow was such a shut-in.”

     Again, everything Ryan said fit with the whole alien theory. Beckett rubbed her temple, trying to block out the questions and worries pounding inside her head. She needed to focus on the case. “Right. Run a background check on that library assistant Mindy, and try to find out from her if Karrow had any other favorite haunts. A movie theater, a bar, a grocery store, I don’t care. Just get me something. The guy has to have interacted with more than one person outside his family. This is getting ridiculous. Meanwhile, I’m going to call Detective Cage from the other day. John Smith is our best suspect at the moment; maybe she got him to talk.”

     Esposito and Ryan nodded and turned to their computers. They didn’t seem suspicious at all. Beckett let out the breath she’d been holding. Normally she wouldn’t shut those two out of anything, but the fact that aliens existed and were involved with the case seemed a bit too much to dump on them so suddenly.

     She made a point of picking up her cell phone so Esposito and Ryan could see, even as she dialed in Castle’s number. “Detective Kate Beckett, badge number 0034, I’d like to speak to Detective Melody Cage?”

     A tired, groggy voice answered her. “ _Castle’s already heading over to the precinct,_ " River told her with a yawn. " _I assume you want us to come too? Damn it, is there any coffee in this house?!_ ” There was laughter in the background, and River's voice dropped to an irritable growl. " _Zip it, sweetie._ "

     Beckett held back a chuckle waited a few moments as though being patched through to the detective. After a few moments she continued. “Cage, have you had any luck with Smith?”

     “ _Oh, more than you know,_ ” River chuckled  sleepily, amidst the loud protest of “ _River!_ ” from the Doctor in the background. “ _We’ll head over in a few minutes,_ ” she continued in a slightly more awake tone.

     Beckett nodded. “If you’re sure… alright, bring him in.” She hung up, trying to hide her amused smirk. Clearly River was not a morning person 

     Esposito and Ryan had turned back to face her, curious. “Is she brining Smith here?” Ryan asked.

     The detective nodded in response. “Apparently her precinct is willing to drop the charges if Smith agrees to help with the case. They say he’s some sort of coronary genius, so he might be able to tell us what’s up with Karrow’s results.”

     Esposito and Ryan shared a confused look. “What was wrong with Karrow’s results?” Ryan asked.

     Beckett cursed internally. She’d forgotten that she hadn’t mentioned that to either of them. “Apparently something was up with his genetic structure. Lanie thought it be caused by drugs but she wasn’t sure which ones,” she lied quickly. Well, it wasn’t a total lie. “Cage is going to bring Smith in to take a closer look. Let Lanie know we’re coming, alright?”

     After another weird look at Beckett, the two turned back to their computers to comply.

SCENEBREAK

     Castle arrived a few minutes later, coffee in hand for his partner. Beckett accepted it with a grateful smile. “I called Cage,” she informed him with a meaningful look. “She’s bringing Smith in to help with Karrow’s results.”

     Castle nodded his understanding as he lowered himself into his chair. They shared a quick look that varied in excitement and apprehension. If Cage or Smith was found out, they’d both be facing trouble. Beyond that, Beckett was still having moral reservations about bringing two liars and possible suspects in under false pretenses. Just because they showed up with a wonderful time machine and stories of other worlds didn’t mean they weren’t mixed up in Karrow’s murder. Beckett defended her actions by reminding herself antagonizing them at all might chase them away in that blue box of theirs, and there would be no way for her to stop them.

     And yet, oddly, Beckett felt herself trusting them. That strange Time Lord and his vicious partner. After she and Castle had discovered the TARDIS, the two travelers had been nothing but open about their intentions and who they were. But more than that, there was simply something so sincere about the Doctor. He might not always tell the truth, but Beckett could see from what he did that he really, truly cared. He truly felt responsible for Karrow’s murder, and he truly felt remorse for a lost life he hadn’t even known. That, more than anything, earned him Beckett’s respect.

     She only hoped she wasn’t wrong.

SCENEBREAK

     They only had to wait a few minutes for River and the Doctor to arrive. The archaeologist was professionally dressed, but her smirk was anything but as she strode into the precinct with her partner in tow. The Doctor on the other hand was in the same tweed-and-bow-tie look as ever. Beckett wondered briefly if he ever changed, but soon snapped into a brisk, professional manner. “Detective Cage,” she greeted as she briskly shook River’s hand.

     The archaeologist’s eyes gleamed with amusement. “Detective Beckett.” She gestured back to the Doctor, who was gazing around the precinct with that child-like curiousity. “Dr. Smith has agreed to look over Karrow’s results to see what conclusions he can draw if you agree to drop any charges against him,” she explained.

     Beckett clenched her jaw, still not at ease with what she was doing. “Agreed. Follow me.” Ignoring Esposito and Ryan, who were gaping at her easy acceptance of River’s terms, turned and led River and the Doctor to the morgue.

     Lanie was waiting when they got there. “Ah, so this is the prime suspect you’ve decided to bring to my morgue,” she commented drily, giving River and the Doctor a measuring glance.

     River stopped to introduce herself, but the Doctor was too distracted by what he saw in the morgue. He gazed around with childlike wonder, a huge grin on his face, and it wasn’t long until he was bounding back and forth, babbling excitedly about the different equipment in the lab. Lanie stared with raised eyebrows at the childish antics, but River just rolled her eyes. “Dear, can we focus on the case please?”

     The Doctor paused, calming down. “Case. Right.” He followed Lanie to the microscope where she had placed Karrow’s tissue sample. As he examined it, Lanie explained uncertainly, “It’s not like anything I’ve seen before. It’s like he rewrote his entire genetic structure. Do you know anything that might have caused this Dr. Smith? Cause I’ve got nothing.”

     The Doctor looked through the microscope, frowning. “Hmm. No, there’s no technology that could do that, not except on the TARDIS, and that’s specifically designed for Time Lord use.” Lanie’s eyebrows rose even higher. She shared a glance with Beckett asking, _Did you bring a crazy guy in my morgue?_ but Beckett could only shrug back helplessly. How could she tell her friend that she knew exactly what the Doctor was talking about, and that it related to aliens?

     The Doctor adjusted the microscope slightly, frowning further. “The problem is, I don’t recognize this. But… hold on…” Suddenly he let out a cry of triumph and clasped his hands together excitedly. He straightened and turned to a bewildered Lanie. “Show me the body,” he ordered eagerly.

     Eyebrows still raised skyward, Lanie turned to wheel out Karrow’s body, still respectfully covered with his sheet. The Doctor grinned when he saw it. “I knew it,” he gushed. He took out his sonic screwdriver, and before Beckett could stop him, he pointed it at the body and turned it on with a brisk _whirr_.

     The body immediately changed. What had once looked human morphed into something distinctly alien. It was shorter than a human, maybe four feet tall, with gray-brown skin that was weathered like an elephant’s that stretched all over its skinny body. It had long limbs, large four-fingered hands, a square-ish jaw, short forehead, tall, pointed ears like an elf with a smaller second ear behind that, wide brown eyes which were larger than a human’s, an extra set of tiny eyes beside those, and a rounded, ape-like muzzle. It was alien but not repulsive, just… different.

     Lanie let out a strangled noise of surprise which remarkably hadn’t turned into a scream, Castle looked ready to burst with excitement, and River looked concerned for Lanie. But Beckett was focused on the Doctor, who didn’t even seem to notice the others’ reactions. He pocketed his screwdriver again, a satifised grin on his face. “He didn’t change his genetic structure from human to alien, he was an alien wearing a shimmer to appear human. Of course his genetic structure was still alien underneath, the shimmer only effects appearance, not DNA.”

     Lanie gaped helplessly at the Doctor, lost completely for words, for once. She was just gathering her words when a small cough sounded behind them.

     They all turned to see a wide-eyed Ryan and Esposito standing behind them, gawking at the body in shock. Ryan opened and closed his mouth a few times, but Esposito was the first to get words out. “Did… did that body just… change?” he asked weakly.

SCENEBREAK

     While the Doctor and River quickly reset the shimmer on the body, Beckett sat Esposito, Ryan, and Lanie down and explained the whole story. How the Doctor, and apparently Karrow, were aliens from another world. How the Doctor and River traveled in a blue box called the TARDIS that could travel in time and space. How they were here to help with the case, and thought they could find an explanation. Esposito took a bit more convincing than Ryan, but seeing the body change seemed to be enough for them in the end. As the shock began to wear off, they both seemed to acknowledge the awesome side of what had happened. In a few minutes time they were questioning the Doctor, Ryan eagerly, Esposito still trying to keep up his gruff tough-guy act.

     Lanie, once the initial shock had worn off, accepted what had happened almost immediately. “I knew there was something weird going on with that DNA.” She gave a nervous laugh, shaking her head at the situation. “I mean, aliens and time travel, that’s all weird and everything, but it does explain what I found.” She quickly seemed to be regaining confidence, although the revelation of aliens still had her a little dazed. “So where’s Karrow from then?”

     “No idea!” The Doctor hurried over from where he had been talking to Ryan and Esposito. “I’ve never met his species. I’d have to run a few tests to figure out exactly what he is, but I think there’s an easier way. We could just pop over and talk to his family.” He was rubbing his hands together with eagerness. “A whole family of aliens hiding out in New York City! Of course it’s not that shocking, New York attracts all kinds, but still, this is early for alien refugees to hang out on Earth. So, the question is, _what_ exactly they’re doing here, _how_ they got there, and _why_ there’s a blade-wielding maniac after them.” His grin contradicted his words.

     Esposito, who had followed the Doctor back over to the group, spoke up. “They could be running from something.” When the others looked questioningly at him, he clarified, “I don’t know anything about this weird alien shit, but I do know that one guy and a few kids aren’t going to take over the planet. They could be running from their planet or some trouble they found there.” He paused for a second, then shook his head, laughing a little bitterly. “God, what am I even talking about?”

     The Doctor clapped his hands, eyes bright. “Good, good idea! So, aliens running from other aliens, and they come to Earth. Why?”

     Beckett almost got the feeling that he was testing them, which irked her a bit, but an answer had already come to her head. “Because we’re not advanced enough to find them.”

     “If they’re advanced enough to disguise themselves as humans, they’d be completely safe,” Castle added, taking up Beckett’s train of thought. “We don’t have any knowledge of aliens yet, so we’d never suspect them of anything.”

     Beckett finished, “And this is one of the largest cities in a relatively lax country as far as civil rights goes. Hiding in a crowd.”

     The Time Lord looked delighted. “Brilliant! So we’re going to find a small family, probably refugees, scared and hiding, especially now that it’s just the kids left. We’ll need to be delicate.”

     Beckett took control once again. “Alright, then just the four of us. Esposito, Ryan, try to figure out how to keep this from Gates. She’ll be expecting an update soon, but if the killer’s alien it’s not likely we’ll be able to arrest them.” She shot the Doctor a glance at that, wondering exactly what his plan was for the killer, but he didn’t say anything. “Lanie, keep looking at that throat wound. Search for anything that might have gotten left behind, a fragment of metal or something. Keep trying to figure out what caused it.”

     Ryan looked a little put out at being told to stay put when there were aliens to meet. “Why can’t we come too?” he asked.

     The detective sighed impatiently. “Karrow’s oldest daughter is protective enough of her family as it is. We need as few people to come with us as possible. I’m coming because this is my case and I have questions I need to ask her, Castle’s coming because he’s good at interrogation and he’s good with kids, the Doctor’s coming because he can disable that shimmer thing and he knows about aliens, and River’s coming because she keeps the Doctor from putting his foot in his mouth." Castle let out an amused snort at this, while the Doctor turned a pout on Beckett, who stared back, unimpressed.

     As she stood up, she fixed everyone in the room with an unwavering glare. In a low, serious voice she told them, "No mention of aliens or time travel or anything we've discussed today will leave this room. We don't know what it is we're dealing with, and if we tell the higher-ups about this, they'll take the case, and they'll take the Karrows, and we'll never see any of them again. We're homicide detective's. We're here to find a killer and being some closure to the victim's family. I'll be damned if I let the victim and his family get carted away to some secret because we thought someone else had to know about this."

     She would have added some sort of threat to the end of this, but there was no need. Lanie still looked shaken, but she cast a quick, sad glance at the victim's body and gave a firm nod. Esposito and Ryan were looking straight at Beckett with calm, determined expressions. Beckett knew they'd attack this case with everything they had now that the stakes were so much higher, and they'd never turn their back on a grieving, vulnerable family. River and the Doctor nodded with unusual solemnity, both looking at the victim with quiet sympathy. Beckett took in their expressions with a critical eye, then finally relaxed. They were outsiders as much as the Karrows. They wouldn't tell.

     Castle reached out a hand, which Beckett grasped gratefully. She didn't even need to ask Castle his confirmation. That man would do whatever it took to protect this family, and he would never betray her, not even to tell his family. For a moment Beckett was almost overwhelmed by the knowledge of just how much Castle loved her, and how much she had grown to love and trust him.

     She turned away from her team and headed for the door. "Alright then. Let's get back to work."

**Notes for the Chapter:**

> Another chapter for you all (or rather my one regular reviewer - thank you superlc529) in which I discover that the Doctor is hard to write (again), this chapter and the next definitely needed to be in Beckett's point of view so it's a good thing I switched, and River is not a morning person. And I'm guessing the Doctor once had to learn that the hard way.
> 
> So now we know Karrow's definitely an alien, and we know he was using a shimmer like the cacti-people (sorry, blanking on their names) from the End of Time. But we don't know what he is, why he's here, or why he was killed. Dun dun dun. Next chapter we'll be returning to the Karrows, which I've been looking forward to for a while.


	6. The Refugees

**Summary for the Chapter:**

> The team meet the Karrows and finally get their story.

On the ride to the Karrows', the Doctor and Castle kept up an amiable conversation, but River wasn't paying attention to them. She was focused on their driver. Detective Kate Beckett.

The detective intrigued her. She seemed at first glance to be a strictly by-the-book toeing-the-line cop. A mindless foot solider of a bigger corporation. But no, in only two days she'd proved to be so much more. Her mistake had been in thinking the detective was driven by rules and a paycheck. But in truth, she was like the Doctor, and in more ways than one. She was driven by guilt, yes, and grief, but it was more than that.

Beckett did what she did for the victims and their families. She was utterly, unshakeable determined to bring closure to others when she herself could find none. And nothing, not aliens or flaming swords or time travel, would get in the way of that.

River's respect for the woman was increasing rapidly, especially after her performance in the morgue. She really wasn't interested in self-gain or even just unburdening herself with the monumental knowledge of alien life and possible invasion. All she cared about was keeping innocents safe. That took serious guts. She was a clear leader as well. The way the two detectives had looked at her, it was clear they respected her.

And yet she wasn't alone. River cast a quick glance at the writer wrapped up in eager conversation with her husband. Richard Castle, the writer who met a pretty detective and decided to play cop to impress her. That was what she'd gathered from what the Doctor had first told her about him. Her own first impressions were that he seemed like Beckett's companion, the one who tagged along and helped.

But then she'd seen them together in the TARDIS. Beckett had been scared, scared of going insane if what she was seeing was wrong, and scared of what it meant if what she was seeing was right. Through that fear, she person she had trusted to ground her was Castle. She had trusted his judgement completely. That went beyond a simple friendship. There was something deep between those two. And earlier, in the morgue, with the two of them sitting together, River had seen the look that passed between them. Caslte wasn't just a tagalong; they were partners. The by-the-book detective and the goofball writer. Two people so different, but from what River had seen between the two of them, they fit each other almost perfectly. Two halves of a whole.

Their dynamic was intriguing, and not so different from her own relationship with the Doctor. She would have to watch them more closely. There was more to be learned about those two.

SCENEBREAK

There was no answer at the door of the Karrows. The lights were out inside, and it had all the presence of being vacant. But Beckett knew better.

"Tanya?" She gave the door another few knocks, glancing casually at the open window. "Tanya, it's Detective Beckett, open up." Castle, River, and the Doctor stood silently behind her.

Still no answer. Beckett checked to make sure no one else was nearby, then called out, "Tanya, I know you're in there. We checked about your aunt, and we found out someone hacked our system and changed things around. There is no aunt. Someone made a fake bank account and file for her." No response.

Beckett's voice dropped to a lower, softer tone. "Tanya, I'm not here to take you or your brothers away. I want to help. I know about your... situation." There was a muted sound from inside, but them silence fell again. "I can't come in here without a warrant unless you let me in. But if I bring a warrant into this then the foster service is going to realize you're living here alone, and I won't be able to do anything about it. I'm trying to help you, Tanya. Let me in."

The silence stretched on for several moments. Finally, the sound of a lock being opened was heard. Beckett let out the breath she'd been holding and shared a quick, relieved glance with Castle. The door pulled back a little, and Tanya's face looked out, much more scared than before. "What do you want?" she asked hoarsely.

"To find your dad's killer," Beckett said simply.

Tanya looked at them warily with those strange gray eyes of hers, but finally she opened the door fully and let them in. When all four adults were inside she closed the door quickly behind them, locking it again, before turning back to her visitors. She leaned against the door, arms crossed defiantly in front of her chest, but with none of the fire she'd had in their last visit. "You know about our 'situation?'" she asked with a dull attempt at a sharp tone.

Beckett relaxed her shoulders, trying to appear as non-offensive as she could. Castle backed off a few paces, gesturing for River and the Doctor to do the same. The two time travelers were regarding the girl with mixed sympathy and interest.

The detective explained gently, "We know that you're aliens." Tanya's eyes widened slightly, but then she relaxed into a defeated slump, her eyes going dull. "We're not here to cart you away to any secret labs, Tanya. I'm not a scientist, I'm a cop. I'm here to solve a murder."

Tanya's eyes widened in surprise, and she let out an incredulous laugh. "Wait, back up. You find a family of aliens, one who's been killed, and you're more worried about a murder investigation?" Then her eyes dulled again. She shook her head sadly. "Oh, just give it up, detective. You'll never catch them."

Beckett and Castle shared a look. "'Them.' So you know who it is?" Castle asked.

Tanya looked at him searchingly for a moment. She had just opened her mouth to answer when her little twin brothers came running into the room, the older John following more slowly. The two redheaded twins slowed when they saw the strangers, then hurried to hide behind their sister's legs, peeking out fearfully. "Tanya, you said we weren't s'pposed to let people in," little Erik whispered.

Ron nodded. "You said they'd take us away from you." His voice went quiet and fearful at the thought.

John hurried to stand by his sister's side, squaring his shoulders in an attempt to look brave. "Who are you?" he asked boldly. He was trembling a little, but he stood firm by his older sister.

Beckett crouched down to be at the twins' eye level. "I'm not taking anyone away," she said gently. "I'm here to help. My name is Kate, and this is Rick, River, and the Doctor."

The Doctor took a step forward. "Don't worry, I'm not human either. But I really think introductions should go both ways." He pulled out his sonic screwdriver for Tanya to see. "Do you mind?"

Tanya hesitated for a moment, then sighed. "Fine. Have at it."

The Doctor waved the screwdriver at the children like a wand. The change was instantaneous. One moment with was a girl and some redheaded boys staring at them, the next there were three miniature Karrows. John looked almost like a shorter version of his father, but the twins had slightly paler skin and darker spots on their face, wrists, and ankles.

Except for Tanya. When the screwdriver waved over her, nothing had changed. There was still a thin, light brunette girl with strange gray eyes standing protectively in front her her alien brothers. The Doctor frowned in confusion, then gave her a quick scan with the screwdriver. His eyebrows went up in surprise. "Huh. No shimmer."

Tanya gave a little mock bow. "Tanya Pierce, full-blooded human, at your service." She paused thoughtfully. "Well, I say full-blooded. I think I mighta had a few aliens thrown in my family line somewhere. I never met my great-grandfather, but I think I got his eyes."

The strange gray, almost silvery eyes glared out at them with slightly more fire. Beckett could see she was gaining confidence since they hadn't called in any scientists or government. Gently she asked, "Can you tell us where you and your family are from?"

"And why anyone would want to hurt you?" Castle added.

Tanya tensed, but finally nodded. "Alright. Let's sit down though, this could take a while."

SCENEBREAK

"I was born on a distant colony in the 51st century," Tanya explained quietly. They were seated on the two couches in the living room. Tanya sat in the corner across from Castle and Beckett, while River and the Doctor watched from the other couch. There was a haunted look in the girl's silver eyes as she continued, "My parents died when I was only a kid. I found out more about them and my family by hacking into their records than I ever did when they were alive. All I knew for the first few years was that they were poor and they'd left me poorer, with debts to pay to some not nice people." Her eyes hardened for a moment.

River spoke up. "You hacked into their records?" Far from being accusing, she sounded impressed.

Tanya smirked. "Yep. I've always been good with computers." She looked down at her hands for a moment, her smile fading. "My parents weren't exactly respectable, and they'd owed some serious people. I had to learn to pay off those people and live on my own. So I did. I lived on the streets, I figured out how scrounge out the right kinds of jobs, and I learned quick. I learned the hard way what happened if I didn't pay up."

She took a deep, shaky breath and lifted her head again. "I finally managed to get out of debt, but once you get into that kind of life you can never really leave. I kept taking jobs - or just plain stealing what I needed if times got bad - and I kept myself alive. I had it better than some. I know my way around a computer. I taught myself how to hack into files, which got me money sometimes, but only if I was careful."

The girl sighed. "Well, I wasn't careful enough. I'd been caught for some minor convictions here and there, and I'd never been fully charged, but those minor convictions were starting to pile up, so by the time they caught me extracting money from a rather wealthy contractor's account, they had enough on me to put me away for a long time. So I ran."

"How?" the Doctor asked curiously.

In response, Tanya slid back her sleeve to reveal a strange sort of wristband. Beckett didn't know what it was, but the Doctor and River seemed to recognize it. Tanya noticed the detective's confusion and explained, "It's a vortex manipulator. It can let you travel through time in space."

The Doctor started to protest scornfully, "That's not _time travel,_ " but River _shushed_ him impatiently.

Tanya slid her sleeve back down and continued, "I'd nicked it off a time agent a while back, but it was really beaten-up when I got it. I’d been working on it for a while, but this is probably the most complicated bit of tech I’d ever found. It took ages to even get it partially working again. It wasn’t finished by the time the cops came after me, but it was my only shot, so I used it to escape. It worked, thank God, but it burned it right out. I fixed it a bit, but it’s not safe to use for time or space travel.”

Her expression softened into the first smile Beckett had seen her give. “I was transported to 21st century, on a little planet called Akali. It’s not too far from here, just three solar systems over. It’s only about half Earth’s size, but it’s so beautiful there.” Her smile grew sad and wistful for a moment. She took a deep breath and continued, “There are so many species who live there, but the only intelligent ones were a species called the Arondrians. They lived in small communities, mostly only interacting with family, but they were a peaceful race. They lived in caves that had been carved in the most beautiful arches and shapes, and they lived on the fruits and plants that grew in the forests. Oh, the forests were wonderful. Trees that stretched up as far as the eye could see, great meadows, huge plants, and little brooks. It was so different from the world I’d come from. And that’s where I met Tikrah and his family.”

Beckett’s brow furrowed for a moment. “Who’s Tikrah?”

“Tikrah. Tim Karrow. I had to come up with a fake name for him, but I didn’t want it to be too different from his real name.” She gestured to her brothers, who were sitting in the kitchen, John talking to his younger brothers in an attempt to distract them from the strangers. “John’s name is Jonora, and Erik and Ron are Irie and Ren.”

“I’d come to Akali expecting to have to keep running, keep stealing, keep living the same life, but I was so wrong. There aren’t any streets on Akali, just forests and caves. I was wandering, lost and starving, when Tikrah found me. They’d never seen a human before, but he didn’t even question me. He took me straight to his family cave and introduced me to his children and his wife, Riiara. They were so welcoming. They gave me food and they said I could stay with them as long as I needed.” Her voice began to waver slightly. “They… they didn’t even question me, not even for a second. They just trusted me and took me in. And now they’re gone.” Her lip trembled, and tears threatened to spill over in her eyes.

Beckett knew she needed to distract Tanya so she could get her emotions in check again. “Did they know how to fix your vortex manipulator?” she asked quietly. A random question to be sure, but it would distract the girl.

Tanya looked surprised at the question, but with a quick sniffle she got a hold of herself. “No, they’re weren’t a technology-based culture. They were vegetarians – what did they need hunting tools for? They harvested the plants they found in the forest. No, they had no need of technology. They were more interested in stories and self-discovery. The Arondrian race was much more open about their feelings than humans. That’s not to say they were always honest. No, it’s more like they valued the discovery and the harvesting of someone’s true self more than any species I’ve met. They would have long, in-depth conversations just about how they felt and what they thought it really meant about themselves. It wasn’t religious or anything, they didn’t believe in some great spirit that determined everything, they just thought that knowing your own self was the most important thing you could have.”

She gave a slight chuckle. “And oh, the stories they could tell! They may not be able to work technology, but they weren’t stupid, far from it. They came up with so many fantastic tales. Creatures from other worlds, legends passed down from their culture, made-up tales of their own lives. And the things they could do with plants. They were fantastic healers, and they knew enough of science that they were starting to create their own plants. It was incredible. And they let me be a part of it without any questions. They adopted me.”

The girl’s eyes hardened, and that hatred from the day before blazed in her eyes. “I had been there a year when the Fatorins came. An advanced species of alien who’d lost their home world in some war or other. They came in their ships and they met with the Arondrians. They said they weren’t trying to invade, they just wanted to share the space. A planet to host two species. The Arondrians accepted. Of course they did, they never could turn away anyone in need. And for a while things went well.” 

“But then a new Fatorin took leadership. _Raktor_.” She spat his name out like a curse. “He believed that the Fatorins should have total control of Akali, and that they had the right to drive the Arondrians out. He soon had an army to back his words. It… wasn’t a long war. The Arondrians had never had to fight before, and they didn’t have any form of weapons. It was over in a few weeks. The entire Arondrian race, gone.”

Tanya gulped, eyes watering. “Riiara was killed early on. After that, I knew Akali wasn’t safe anymore. So I took my family and we escaped. The Fatorins had these small combat ships they used to attack. I was able to commandeer one, which I used to get my family out. We… we had to walk through the battle fields to get there. Irie and Rie were asleep, they didn’t see anything. I tried to keep Jonora from seeing too much, but I think he still remember. It was… horrible. So many dead, just lying there, gone.” She blinked back more tears.

Beckett reached out to grasp Tanya’s trembling hands. “I’m sorry, Tanya. I truly am.” She and Castle shared a sad, horrified glance. The detective knew how much it felt like a knife to the gut whenever she looked at that picture of her mom in that alleyway. But to see an entire species, the one that adopted you, bleeding their lives out in front of you? She couldn’t imagine how horrible that had to be. A quick glance at River showed her to look horrified and sympathetic, but the Doctor didn’t seem surprised at all, just dully, tiredly sad. There was sympathy there too, and a deep, deep pain. _He lost his species too,_ Beckett remembered sadly.

Tanya took a shaky breath and gave Beckett a weak smile. “Thanks.” She didn’t draw her hands back as she continued, “I was able to bring them here to Earth. We crashed way out in the woods, no one saw us come down, at least I don’t think so. We wandered for a bit, but finally we were able to find a town where they had computers I could hack into. I set up an identity for us as the Karrow family and got us a one-way ticket to the most crowded place I could find – the great city of New York.” Her voice became mocking on that last bit. “It was hard for all of them, especially Tikrah. It was so ugly here, so noisy, so crowded. Bit of a culture shock. And he’d lost his wife. I really thought it was going to kill him for a while, but he pulled through for me and for the boys. I got him a quiet little shop where he could sell and read stories all day. I hired Mindy to help with the financial stuff, Tikrah was never really good at that. I constructed an entire backstory and got our files to stretch back for years and years. Honestly, it wasn’t that difficult, 21st century technology is a breeze after everything I’ve seen in the 51st century. But I was always worried that I’d left something out, that it wasn’t detailed enough, that we’d be found out.”

Beckett remembered something from earlier. “Esposito said Kar- Tikrah didn’t have any medical records.”

The girl let out a snort. “Knew I’d forgotten something,” she sighed. “We were fine for two years. The boys had some trouble at school, but I was able to help out. We grew as plants at home and we read the stories of this world. We were happy.”

She trailed off, fear coming back into her eyes. Beckett waited a few moments, then prompted her gently, “What happened?”

“I saw one.” Tanya whispered. “A Fatorin, just for a few seconds in the shadows of an alley, but I saw it. It was shuffling around, growling like an animal. I ran back home as fast as I could to make sure everyone was alright, and I told Tikrah what I saw. He thought I’d imagined it, he thought that we were safe, that _I_ had made us safe… if I could have convinced him to hide…” She paused, unable to go on.

Castle leaned forward, eyes sympathetic. “So you think this Fatorin came after you and your family?”

Tanya nodded more firmly now. “Yes.” She looked at all four of them in turn, silver eyes going hard and demanding. _You said you’re here to help,_ they seemed to say, _so you better pay up._ “Find the Fatorin, and you’ve found Tikrah’s killer.”

**Notes for the Chapter:**

> I cannot even say how long I've been looking forward to this chapter. I'm really proud of my original characters / aliens / backstory in this one. Especially Tanya. I really hope you guys like the concept I came up with, with the Arondrians and the Fatorins and Akali. All of those names, by the way, come from an old wolf roleplay I used to be part of. I felt the names were awesome enough to use.
> 
> There's more to come, don't worry. There's still a culprit to catch, and more mystery to uncover.


	7. Tracking Suspects

**Summary for the Chapter:**

> The team sets off to find their suspect.

River watched sadly as Tanya went into the kitchen to talk to her brothers. So many innocent people lost, and this little family left to deal with it all. There were times like this that the universe was so unfair River just wanted to scream. She'd seen horrible things in her weird, crazy life. She'd been hurt and she'd hurt back, even killed those whom might not have deserved it. Someone so hardened should be used to unfairness by now, but River couldn't help wishing things had been different for Tanya and her family.

She hadn't even realized she'd sighed until the Doctor turned to her with concern. “Are you okay?” he asked quietly.

River shook herself our of her dreary thoughts. “I'm fine.” She gave her husband a weak smile. “It's just, sometimes you find yourself thinking things were different, you know?”

Something sad sparked in the Doctor's eyes. He had to swallow a few times before he finally whispered, “Yeah, I know.”

River felt a surge of sympathy for the Time Lord. Here he was confronted with a family which was the last of its kind. The kind of memories this had to be bringing back.

River laid a comforting hand on his knee, giving him a sympathetic smile. "It's not your fault, sweetie." The Doctor looked at her, a little surprised, but after a few moments he gave a small, grateful smile. They sat like that for a while, neither speaking, just taking comfort in each other.

Tanya led her brothers in from the kitchen. The twins hurried over to the couch, blinking curiously at Castle and Beckett, but John – Jonora – remained wary. “Tanya, can we trust them? I thought humans had rules about children living with adults.” His voice was only slightly higher than it had been before, and a bit softer.

Tanya nodded. “There's only four of them,” she pointed out. “They could have brought more but they didn't.”

The Doctor gave the boy a cheerful grin. “Don't worry Jonora, I'm pretty well-known with all the alien-related agencies. I can make sure they won't try to lock you up.”

Tanya looked at him, eyes narrowed thoughtfully. “You're not a cop.” It wasn't a question. “Who are you again?”

“I'm the Doctor.”

Ren and Irie looked up, eyes wide with wonder, while Jonora and Tanya blinked in surprise. “ _The_ Doctor?” Jonora asked in a voice tinged with awe. “From the stories?”

The Doctor looked amused at their recognition. “What stories?”

Tanya rolled her eyes. “It's not him, Jonora,” she told her brother. “It can't be. It's just a legend. Stories the Time Agents at the bar used to tell when they'd had a bit too much to drink.”

“Ooo, I love a good legend,” The Doctor said with a bright grin. “Legends are always fun, especially when they're wrong.” His expression sobered slightly. “But I really am the Doctor.”

Tanya raised an eyebrow scornfully. “You're the last of the Time Lords? The man who saves universes?” There was no mistaking the mockery in her voice.

The Doctor flinched from the first part, but nodded. “Well, that's the idea anyway,” he admitted.

“Then where were you?” Tanya's silver eyes were unforgiving. “When my home, my people, were taken, where were you? Hmm? The man who saves universes, where the hell were you when the Arondrians were slaughtered?!”

The Doctor looked stricken by Tanya's accusations. He shrunk away, his eyes far older than they had any right to be. Despite her sympathy for the girl, River felt a surge of protectiveness over her Time Lord. "He can't save everyone, Tanya," she said with a slight edge to her voice. "Some things can't be changed."

Something in Tanya's eyes wavered, and River felt a rush of sympathy. "I'm sorry Tanya, but there's nothing we can do. The war's over. But we can help you now."

The teenager hesitated, then sighed, still tensed uncomfortably. "You'd better," is all she said. Without another word she turned and strode off into the kitchen, Jonora following her worriedly.

Beckett turned to the Doctor with a shaken expression. Clearly Tanya's story had really impacted her. "Is there really nothing you can do?" she asked quietly

With a sigh, the Doctor shook his head. "I can't change an event someone told me about. It cancels out me being told about it... it's all confusing and timey wimey, but in the end there's nothing I can do." There was a defeated slump in his shoulders, and River hated the dull look of pain in his eyes.

Beckett seemed to gather herself up for a moment. In a firmer, serious tone she told the Doctor, "Then it's not your fault. Now I need you to focus now. This family needs our help. Now, what do you know about the Fatorins?"

Beckett's words seemed to shake the Doctor out of his stupor. He straightened, a thoughtful expression on his face, the mournful air of moments before gone. River was privately impressed with how Beckett had handled the Time Lord, even if the effect would only be a temporary distraction from his guilt.

"Fatorins aren't too different from humans," the Doctor said. "But they're a lot more stubborn. Once they get focused on something it's nearly impossible to distract them from it. They live on Akali for several million years after this." He frowned thoughtfully. "Never knew they stole the place, though. Doubt they remembered it themselves by the time I met them."

Castle perked up at this last part. "So you've met them before?"

The Doctor nodded. “In the 38th century. Nice enough place, if a bit politically driven. Not all that different from Earth. I’d heard of Raktor before, but apparently he was some big dictator they’d deposed not too long into his reign. He’d faded into legend long before I’d arrived. The government when I met them was closer to a democracy.”

“Did they have that Tyron Energy thing?” Castle asked curiously. “I thought you said no one had that for years and years.”

The Doctor looked almost guilty. “Erm, yeah, I did say that. And most people don't find tyron energy for quite a few years. But Fatorins and a few other species were slightly ahead of the curve on that one.

River rolled her eyes. “So this whole time we thought we were tracking a time traveler and we're really after a technologically advanced alien?” she asked with a pointed glare.

“Well, I can't be right every time!” the Doctor defended himself indignantly.

Beckett rolled her eyes at the Doctor's forgetfulness, but the look was gone in a moment and the focused detective was back. Calmly she asked, “What do they look like?”

“They’re pretty much human-shaped, but they’ve got dark brown skin, a scrunched up nose like a hog-nosed bat, and little cow ears that stick out from the sides of their head. Oh, and no hair. Kinda wrinkly. Yellow eyes.”

Castle frowned. “Alright, so they’re not going to blend into a crowd easily.”

The Time Lord shrugged. “There are plenty of ways to look human. They could have a shimmer or be wearing a human suit.” His look faded into a reminiscent one. “Or they could have a perception filter like those sexy fish vampires.”

Castle and Beckett looked a little taken aback. The writer seemed on the verge of asking more, but River cleared her throat. “As fun as that story sounds,” she said smoothly, “can we get back to business? The question now is how do we find this Fatorin?”

“Find and question,” Beckett stated firmly. The detective’s gaze was fixed on the gun still in River’s holster on her hip. Clearly, she didn’t trust that the time travelers weren’t planning on killing the culprit once he was caught.

River gave the detective a brief nod. “Find and question,” she affirmed. Beckett seemed to relax, before throwing herself back into what River was increasingly recognizing as her ‘detective mode.’

Castle leaned forward, hands clasped thoughtfully. “So,” he summarized, “we’ve got an alien killer on the loose who may or may not look like a completely random human and may or may not be planning an invasion?”

“Pretty much, yeah,” the Doctor said breezily. “But don’t worry, we’ll find them.”

Beckett scoffed, “How can you be sure?”

The Doctor smiled, jumping to his feet with sudden energy. “Because I’m the Doctor," he said with a smug grin. "If there's one thing in the universe I'm good at, it's finding trouble. Now!" He clasped his hands together eagerly, a manic grin on his face. "We've got to track down an alien with possible transport off this planet, a flaming sword, a possible disguise as a human, and has a deep, murderous grudge against a family of aliens disguised as humans. So where do we start?"

Beckett spoke rapidly. "If they're disguised as human, they've probably got falsified records like Tikrah..."

"... but if they look like aliens they'll be trying to hide somewhere they won't be noticed," Castle continued, picking right up where his partner had left off. "Somewhere secluded..."

"... like that parking lot we found Tikrah in!" Beckett realized, not missing a beat. "The area around there was too open for them to get anywhere without being seen during the day..."

"... and we were there that night..."

"... so unless it left after we left that night..."

"...or before the body was found..."

"... it's still there!" Beckett finished triumphantly.

They turned to the time travelers with triumph, only to see the Doctor blinking bemusedly at them and River snickering quietly. The confusion on the partners' faces only made her laugh harder. "Ooo, that's a fun trick," she remarked, still snickering. "I think I'll have to learn that one. What do you think, dear?" She turned to her husband with a smirk.

The Doctor blinked a few more times before shaking his head. "Humans," he snorted.

River just rolled her eyes. "So he's most likely at that garage, but he could have disguised himself to be human."

"Maybe, but I don't think he did," Castle responded. "Tanya said she'd seen him in Fatorin form."

"Maybe he hadn't activated his shimmer yet," River argued. "Or maybe he was just giving her a warning."

Beckett's brow furrowed. "Yeah, but why would you warn someone you're hunting down?" She mused.

The Doctor perked up. "Unless they weren't hunting them down," he reasoned. "Just coming here to hunt down one little family seems pretty pointless. They've already got the whole planet, haven't they? Maybe they needed something from Tikrah."

"Yeah, but what could they want with him?" Beckett asked. "They destroyed his entire species, what would they need him for?"

The Doctor shrugged. "Could be anything, you know, maybe there's environmental problems with the planet or something, or there's a resistance they think he could stop, or maybe there's more than one Fatorin and this one was trying to warn her."

Beckett stood, soon followed by the rest of the team. “So he could still look human. I'll get Esposito and Ryan to check out the security footage for outside the garage, see if there's anyone there who might be our guy. Doctor, you were able to tell last time that the aunt's records were fake. I need you at the precinct so you can check out files of people on that security footage. River, he doesn't have any clearance without you there, so go with him. Be careful if Gates shows up, Ryan and Esposito aren't the best liars, so help them if you can. Castle and I will check out that parking garage.”

The Doctor looked surprised for a moment, then nodded. “Alrighty then.” He gave his wife a quick smirk. “Come along, Pond,” he joked lightly as they headed for the door, leaving Beckett and Castle behind to say goodbye to the Karrow family.

River was a little surprised at the dynamic they'd fallen into. Usually it was the Doctor taking charge and the human companions following what he said. But the detective was clearly experienced and clever and used to giving the orders. Castle was her partner, yes, but she was the one with actual authority. It was natural for her to take charge of her own investigation.

More surprising was the way the Doctor was doing what he was told. The Time Lord had never exactly been big on authority or following orders. Then again, it wasn't like he was just bowing his head and letting her take over. They had been bouncing ideas back and forth, and she was trusting them on the matter of aliens and time travel. Still, it was an odd situation, and one that she might have to tease him about later.

_If he can remember it,_ she thought sadly.

SCENEBREAK

Beckett turned to Tanya, who was still glaring at them with mistrust and doubt. She lowered her voice to sound as reassuring as she could. “Don't worry Tanya. We're going to find who did this.”

Tanya just snorted disbelievingly. “Yeah, you'll find them alright,” she agreed. “Then they'll kill you, just like they killed Tikrah. They've got technology like you wouldn't believe.”

“We'll be fine,” Beckett assured her. “We've been trained to deal with things like this. We've got guns, and we can handle a guy with a sword.” Privately she was worried about their chances against the Fatorin. She wondered whether she should have kept River with them to have another gun hand, but she and the Doctor were needed more at the precinct. There was no way to call in back-up without things getting awkward, and if the alien was still at the garage they needed to check it out as soon as possible. It would have to be the two of them.

Tanya just shook her head. “You better hope it's just a sword,” she said ominously.

“Hey.” She waited until Tanya finally met her gaze again. “I promise you, Tanya. We're going to find them. I will not let this go unsolved. Alright? And we're going to make sure your family's safe.”

The teenager measured Beckett's gaze, eyes going wide with surprise. “You actually care, don't you?” she asked quietly. “You actually care about avenging Tikrah. Why? What does it matter to you?”

Beckett closed her eyes as fresh memories flooded her mind. A man in a parking lot faded into a woman in an alleyway. Opening them again, she gave Tanya a sad smile. “Cause I've been in your place, and I know how it hurts,” she explained simply.

Tanya blinked in surprise at Beckett's sincerity, then sighed sadly. “I'll hold you to it then,” she said quietly. “Help me keep my family safe.”

“I will,” Beckett promised solemnly. With that, she and Castle said good-bye to the boys and headed out to the car.

Castle seemed to notice how quiet his partner was being. “You okay?” he asked with concern.

The detective let out a breath, the depth of their situation hitting her. “I promised her we'd catch the guy, but what if we can't?” she confided quietly in her partner. She wouldn't have said it with River and the Doctor around. But she could tell Castle anything. He always understood, and he always knew just what to say to make it better. “What if River's right and we're way in over our heads?”

After a few solemn moments to show he understood, Castle gave her a reassuring smile. “We've been outnumbered before and gotten out okay,” he reminded her. “We'll be fine with one alien.”

“And what if it's not just one?” Beckett argued quietly. “What if there's an entire invading force, Castle? This isn't like anything we've dealt with before.”

Castle shook his head calmly. “You know that's not true. This is a murder investigation. It always has been. Someone's died and it's our job to find out who. And from what River was saying, the Doctor's gone up against armies before and won. He can do it again.” His grin turned lopsided as he joked, “The combined forces of the Doctor and the great Detective Beckett. The world won't know what hit it.”

Beckett cracked a smile, her fears fading as she thought about what Castle said. He was right. They needed to focus on the murder, and if it turned out to be bigger than that, they'd deal with that when they got there. “You're right,” she said with more confidence.

“Oh, that reminds me,” Castle said cheerfully, clearly trying to drive the conversation away from the solemn turn it had taken. “I haven't said 'I told you so' yet.” The childish light gleamed in his eyes again. “For once I was completely, one hundred percent right. I so called the Doctor being a time traveler!”

The detective laughed at her partner's antics. Her chest filled with warmth. He always knew how to make her smile. Instead of responding, she just rolled her eyes. “Come on, Castle. We've got an alien to catch.”

SCENEBREAK

Back at the precinct, as the Doctor scanned through the files with his sonic screwdrivers, River had turned her attention to the other partners. Esposito and Ryan still seemed to be coping with the revelation of aliens, but like Beckett they seemed to be forcing themselves past it and throwing themselves into the case. But unlike their leader, that didn't stop them from asking questions.

“So, how's it work? Time travel, I mean.” Esposito was leaning forward with his hands clasped, his curiosity clearly outweighing his unease. Beside him, Ryan looked just as curious.

River laughed quietly. “That's a question for the Doctor I'm afraid. And he doesn't really like to explain that one.” She turned to glance at the man in question, who was scrolling through the computer files with his sonic screwdriver _whirring_ relentlessly. She turned back to the two men with an easy smile. “He says it's because it's way above human comprehension, but I think he just doesn't want to explain the thing that makes him look impressive.”

“Is not,” the Doctor interrupted sullenly from his spot by the computer.

River rolled her eyes. Without looking at him she scolded lightly, “Focus, dear.” She smirked at Esposito's bemused expression.

Ryan, however, was focused more on his next question. “But what about changing events? Like, doesn't changing a small thing make ripple effects that change the future?”

Oh, this one she could answer. She leaned back thoughtfully in her chair. “Not exactly. And not everything in the future is set in stone. Most of time is in flux; anything can happen. And the universe will mostly work to compensate for any small changes, rearranging itself so the future turns out more or less the same. So we're mostly safe changing things in the past. But there are some points which are fixed. They can't be altered, they always happen the same way. The Titanic, Pompeii, Hitler's death. Interfering with events like that could tear the universe apart.”

Ryan looked thoughtful as he processed what River had told him. Esposito took his turn to ask a question. “So what's the future like?”

River raised an eyebrow. “Depends on what year you're asking about. I live in the 51st century. It's pretty nice. Though security guards are rubbish there. Cute enough though.”

Esposito looked surprised. “Security guards?”

“Oh, did I mention? I live in prison.” River explained with a smirk.

Ryan and Esposito seemed a bit taken aback. “What for?” Esposito asked guardedly.

River flinched as she remembered watching her own crime only a week before. Knowing that the Doctor had faked his death hadn't made it any easier to watch. That doubled with the memory of pulling the trigger herself...

The archaeologist shook herself out of her thoughts. “Doesn't matter,” she said quickly. “I'm innocent, sort of, I just stay there cause this idiot,” here she threw a pointed glare at the Doctor, “needs me to. I get out often enough, and it's not a bad place to live.”

Esposito still looked a little suspicious, but Ryan seemed more interested in River's story. “So is police procedure still the same? How do the prisons work?”

River was about to answer when the phone on that partners' rang. Esposito picked it up swiftly. “Esposito,” he greeted. He listened for a few moments, then held the phone out for River. “It's for you,” he told her.

River took the phone. “Yes?”

“ _There's nothing here._ ” Beckett's voice had a slight edge. “ _We checked the whole place, there's nothing. Not a trace. He must have gotten out right after the murder. We've got nothing._ ”

River made a disappointed sound in the back of her throat. Esposito and Ryan looked at her curiously, but she ignored them. “We haven't found anything here either,” she told her. “The Doctor's still looking through the files.”

Beckett sighed. “ _Of course not._ ” There was a long pause, then the detective spoke again. “ _Listen, it's late, we should get some sleep. Castle says you can stay at his place as long as it takes to solve the case. Just grab a cab and head over._ ” The line was cut off, leaving River to deal with a sudden rush of frustration. Usually adventures with the Doctor were so whirlwind that it was hard to keep up. The way this case was dragging on frustrated her to no end. It was all brainwork, this detective stuff. All this waiting around.

Oh well. Work to be done.

River turned to her husband. “Come on sweetie,” she said as she stood. “We'll keep working tomorrow.”

They'd work as long as it took.

**Notes for the Chapter:**

> Urgh, I sort of lost steam at the end, but I think the rest is sort of okay. Blegh. I'll try harder on the next one. Anyway, have some mixed River and Beckett POV. And some Esposito and Ryan awesomeness.


	8. Heart to Heart

**Summary for the Chapter:**

> The two duos uncover more of their lives.

Beckett still seemed a little on edge when they reached Castle's flat. The detective had a set to her jaw that showed her disappointment. The Doctor seemed to notice, because after they all exchanged weary greetings, he put a hand on both her shoulders and looked her in the eyes. "We'll find them, Detective Beckett. That's a promise." 

The detective stiffened at the sudden contact, eyes wide. After a few moments she relaxed slightly before pulling away. “No need to patronize me, Doctor,” she said wearily, no real bitterness behind her words. “We’ll pick it up tomorrow.”

“Oh, hello again,” a familiar voice came from upstairs. Martha Rodgers descended from the stairs, this time with a ginger teenage girl in tow. “I didn’t realize you two would be staying another night.” She swept almost regally into the room, a permanently dramatic air about her. She wasn’t like anyone River had met before, but she found herself liking the actress.

The teenager looked curiously at the time travelers, displaying none of the hostility of Tanya. “Who’s this?” She asked Castle.

The man wrapped an arm around the girl’s shoulder in a completely familiar matter. “Alexis, this is Doctor River Song and her friend the Doctor. We brought them in to help with our case, but they didn’t have anywhere to stay. Doctor, River, this is my daughter Alexis.” For a moment, his arm tightened protectively around the girl, and his eyes gazing at the time travelers suddenly gave a flicker of distrust. _Of course,_ River realized, _we’ve proved ourselves enough for him to trust us for his own sake, but his daughter’s another story._

River forced herself to give a warm smile, holding out a hand for Alexis to shake. “Good to meet you, Alexis,” she greeted the girl, shooting Castle a quick, reassuring glance. “Your dad was very generous to let us stay the night.”

Alexis shook the offered hand with a smile, but she seemed to sense something was being held back. “So, Doctor Song and Doctor…?”

“Just ‘the Doctor.’” The man in question answered, staring at Alexis curiously. “You weren’t here last night,” he remarked in a way that made it seem like a question.

Alexis shrugged, still eyeing the Doctor warily. “I’m just visiting from college,” she explained. “So you actually just call yourself ‘the Doctor?’”

The Time Lord gave an easy nod. “Yes, just the Doctor. Why is everyone surprised that it’s just the Doctor?”

Alexis didn’t answer, instead, giving her father a questioning look. She didn’t seem to distrust the time travelers, but she did seem to realize the whole truth wasn’t being shared. “So what’s the case this time?” she asked instead. “And how are you two helping? Is there something off about the body? The NYPD doesn’t usually get outside help, except for Dad, so you two must be higher ups.”

Ooo, River liked this kid. She was curious, smart, and asking the right questions. She had a feeling Alexis would make a good companion, but she also had the feeling Castle and Beckett would take the Doctor’s head off his shoulders if he ever tried to recruit her. She shook her head with a slight smirk. “Sorry kid, we’re not that kind of doctors. I’m an archaeologist. We’ve been traveling a bit, seen a lot, and we’ve got a lot of experience with this kind of case.” The Doctor let out a slight chuckle, and Castle and Beckett seemed to be holding back smirks at River’s word choice.

Alexis, however, still looked curious, but she seemed to recognize that River wasn’t going to say any more on the matter. “Well, nice to meet you,” she said with a smile, which River returned. Alexis shot her dad a quick glare which seemed to say _I’ll be asking you about this later._ Oh, she definitely liked this kid.

SCENEBREAK

That night, the stories at dinner had to be reigned back a bit. Now that Martha and Alexis were present, River and the Doctor couldn’t exactly bring up aliens and time travel. However, River seemed pretty adept at exchanging planets and species inside a story for ones more plausible for Earth. The stories were undoubtedly still the fantastic tales of their journeys through time and space, they were simply a little more Earth-themed now.

In turn, Beckett and Castle shared some of their more interesting exploits. Beckett was surprised at how interested the time travelers seemed, especially the Doctor. She’d thought after all they’d seen and done, some homicide cases would be a bore to them, but they seemed truly interested in the cases she and Castle related to them.

After a particularly interesting story about a man found hanging under a bridge, Martha turned to a still-laughing River and Doctor. “Well, you two certainly seem to lead an interesting life. How did you two first meet?”

To Beckett’s surprise, River looked suddenly uncertain and sad, while the Doctor stiffened, fierce pain flashing in his eyes for a brief moment. He shook his head slightly, the old smile returning to his features, but somehow it seemed empty. “Spoilers,” was all he would say.

River looked at the Time Lord with something like fear in her eyes before turning back to a bemused Martha. “I was pretty young when I met him,” she said with a slight smirk, as though laughing at a private joke. “I was a pretty rebellious teenager. Oh god, I was always getting in trouble. Then he came along and got me interested in archaeology.”

Martha raised an eyebrow. “Oh? How so?” Beckett held back a smirk. Castle had certainly gotten his talent for sensing good stories from his mother.

River and the Doctor shared an amused glance. “Well, it’s a bit of a long story,” the archaeologist said, choosing each word carefully. “You see, I may or may not have tried to kill him the first time I met him.”

Beckett stiffened in shock. She was sure her face matched the dumbfounded expressions Castle, Alexis, and Martha wore. The cop in her immediately recoiled in distrust, but she forced the instinct back. She’d known River and the Doctor had a colorful past, after all. She just hadn’t been expecting that. A quick memory of “Detective Cage” pointing a gun at them with a feral smile crossed her mind, but she forced it back.

Alexis was the first to speak. “You… tried to kill him?” she asked hesitantly. The unspoken question hung in the air. _Then why are you sitting together now?_

The Doctor grinned cheerfully. “Yes, well, that’s the thing about me, no matter how many times you try to kill me, I always seem to spring back.” Affection, and something deeper, gleamed in his eyes as he turned to River. “She tries to kill me, then saves my life the same day. Bit of mixed signals there. After that, you just couldn’t resist, could you?” For a moment, Beckett was surprised at how openly the Doctor was flirting with his companion, but then she realized River’s smile had faded slightly and her hands were gripping the sides of her chair tightly.

The Doctor’s words finally brought River’s smirk back. “I’m the one who couldn’t resist?” She asked with amusement. “I’m not the one who broke into a military base to save you.”

The Time Lord pouted slightly. “I didn’t know you were there,” he protested, “I was trying to save Amy.”

This time it was Castle who asked the question. “Amy? Who’s Amy?”

The Doctor’s eyes glazed over with sadness, but River seemed more open to talking about it. “Amy and Rory Pond. They’re… friends of ours. We all travel together. Well, they travel with him; I just hitch along whenever something fun’s going on. Or when the Doctor’s gotten himself into something he needs me to get him out of.”

The Time Lord tried to scowl, but an affectionate smile ruined it as he protested, “You’re the one who’s always calling me to help you out.”

Alexis looked between the two, understanding flashing in her eyes. “Where are they now?” She asked gently. “Amy and Rory I mean.”

The Doctor gave a smile that didn’t quite seem to reach his eyes. “They stayed behind. They’re safe at home.”

After a few awkward moments of sympathetic silence, the topic was hastily changed, but Beckett couldn’t help but wonder what the Doctor meant by “left behind.” From what she’d gathered, Amy and Rory were human. What happened to the humans who traveled in the TARDIS? The Doctor had dropped so many names – Ace, Jamie, Martha, Donna, Rose, and now Amy and Rory – but never explained why there seemed to be a different companion for every story. His life seemed to be an exceedingly dangerous one.

Is that what the Doctor did? Pick up someone to ease the loneliness until some danger took them away as well? What was it like to come to care for someone that much and then to lose them over and over again? Subconsciously she reached out for Castle’s hand, only relaxing when he took the offered hand. _I’m not losing you like that,_ Beckett thought fiercely. _Not ever._

SCENEBREAK

After dinner, Alexis and Martha excused themselves for the night. The Doctor had headed into the still-invisible TARDIS to tinker with something, so Beckett and Castle took the opportunity to question River. “What was the Doctor talking about with ‘spoilers’ earlier?” Castle asked curiously.

River let out a sigh. They were all seated on the couch in the living room, with the partners both turned to face the archaeologist. She looked up at the partners with a sad smile. “I told you earlier that I don’t travel with the Doctor permanently, I just come along sometimes.” At Beckett and Castle’s nod she continued, “Well, he’s a time traveler. We don’t always meet at the right time on each other’s timelines. Sometimes he’s come to pick me up and it’ll be the same Doctor I had an adventure with a few days ago, and sometimes it’s a Doctor who’s only met me a few times and doesn’t really know who I am.” The woman leaned back against the couch with an unusual air of sadness. “There are adventures we’ve shared that he hasn’t lived through yet. So many memories I can’t share with him because they’re still in his future. And the same goes for me. I’ve never lived through the first day he met me.

Beckett’s eyebrows went up in surprise. And she’d thought her relationship with Castle was complicated. “So sometimes you have to meet a version of the Doctor who doesn’t know you?”

River just gave the same sad smile. “Life with a time traveler,” she said quietly. “His past in my future. Every time I meet him he knows me less.”

Castle cast a glance at the place where the invisible TARDIS rested. “What about this version? He seems to know you pretty well.”

River’s expression softened, and warmth lit up her eyes. “Yes. He knows me pretty well right now. He knows who I really am, and he knows my secrets. But there’s still so much we haven’t lived through together. And one day I’ll lose him forever.” That fear from earlier filled her eyes again. “One day, I’ll have to live through that first meeting. The day the Doctor looks at me and doesn’t have the faintest idea who I am. He’ll never have met me at all, and I’ll be stuck with all the memories I can’t share, knowing that I’ll probably never see him again.”

Beckett found there was nothing she could say to that. What could possibly be said to make something like that better? To live with that kind of countdown, knowing the end was coming and there was nothing you could do to stop it…

Unconsciously, Beckett shuffled a little closer to Castle, leaning back against his shoulder. They may have wasted four years, but at least they had all their futures stretching out ahead of them, to use as they wished. River didn’t even have that.

A few moments of silence passed before River spoke up again. “Alright, as long as we’re having this little heart-to-heart, what about you two? You’re obviously together, but what’s the story there?” She cast a pointed look at the way Beckett was almost snuggled up against Castle.

She shuffled away a little self-consciously, but there was no reason to hide anything from River. “Yeah,” she said simply.

Castle gave a warm smile. “We’ve been together a few months.”

Beckett looked down at her hands for a second, avoiding River’s gaze. Their relationship wasn’t something they really talked to other people about. “Coworkers aren’t really supposed to date,” she explained a little awkwardly. “We’ve been keeping it a secret.”

River nodded in understanding. “Ah, forbidden romance. Fun stuff.” Her gaze seemed far too knowing for Beckett’s liking.

Eager to move the conversation away from them, Beckett asked, “So what’s it like traveling with the Doctor? Going anywhere and anywhen?”

River leaned back against the couch with a wistful, slightly awed smile. “Traveling with that man is like flying. I wish there was a better way to say it. You can go anywhere, meet anyone, touch any star, tied to nothing and no one. You can save galaxies, become a hero, actually change lives. And all in the company of that mad, brilliant man and his box.”

She gave Beckett a quick, knowing look. “I know you’ve been wondering about all his companions. He’s dropped a lot of names, more than he usually does. He’s lived over a thousand years and picked up so many friends to travel with, and lost them all. Life with the Doctor is extremely dangerous. I won’t lie and say it’s not. Some companions die, some are lost, and some leave for their own safety. I can get wondering why anyone would want to choose that life.” She smiled as she cast a loving glance at where the invisible TARDIS sat. “But to see all those stars, all those skies, and to run with that man, is one life really such a price to pay?”

River’s words painted wonderful pictures of far-off worlds and long-lost sights. Beckett was spellbound in a way she seldom was. The life River was describing seemed almost too good to be true. To be able to go anywhere, help anyone who needed it, save as many lives as time could hold…

Wasn’t that, deep down, what she really wanted?

SCENEBREAK

The next morning woke Castle later than he usually woke. He lifted a groggy head, wincing as the early morning light hit his eyes. Vaguely he wondered why he felt so tired, before remembering. River’s words last night had inspired him so thoroughly that he’d had to write. He’d stayed up a better part of the night furiously typing all the fantastic words and ideas that swam in his head. Distant worlds, fantastic creatures, the company of a god who acted like a child. Of course, he didn’t reference any of River or the Doctor’s stories directly. He wasn’t even sure he was going to use any of it for any book. He’d just needed to get it all down and let his imagination run away for a bit. And now it was all down if he ever felt inspired to finish it.

At the heart of it all was the tragic story of River and the Doctor. Two people tied together by love, but never truly together, losing each other day by day. A true tragedy. Castle had explored the consequences of such a story through his writing last night, and no ending he could see could lead to either being happy.

Internally cursing himself for staying up so late, Castle forced himself out of bed and onto his feet. When he went out into the kitchen, all he found was a note saying Beckett, River, and the Doctor had already left for the precinct.

“Hey Dad.” Castle turned to see Alexis coming down the stairs behind him.

“Hey,” Castle greeted warmly, wrapping his daughter up in a quick hug. “What are you doing up so early?”

“I wanted to catch you before you left.” The redhead hesitated for a moment. “Dad, is there a reason you don’t want to talk about this case?”

Castle stiffened, then turned to the fridge hurriedly, not looking at his daughter. “Who says that I don’t want to talk about it?”

Alexis rolled her eyes. “Dad, please. You wouldn’t answer any of our questions about it last night. You just passed them off or ignored them. You always tell us about your cases. So what’s going on? The doctors didn’t look like government officials, but they wouldn’t say anything either.”

It was times like these that Castle wished his daughter were just slightly less brilliant. He loved her, but it was hell trying to lie to her. He tried to make his voice casual as he told her, “It’s nothing, really. Some of the circumstances were a little weird and Gates wants us to keep it close to the chest. And I really don’t want to piss her off more than I already have to.” He mentally thanked Gates for providing a good excuse for his silence.

Alexis’s brow crinkled. “Weird how?”

Castle scanned his brain desperately for something. “Like it was professional. The vic might’ve been mixed up in some really tangled political thing. It’s complicated, and I’m sorry, but I really can’t tell you.”

Alexis looked at him searchingly for a few more moments before sighing. “Alright. Just stay safe, alright?”

Castle smiled. “I promise.”

As Alexis turned to the kitchen to get her food, Castle thought about what River had said the night before. “ _Life with the Doctor is extremely dangerous. I won’t lie to you and say it isn’t._ ” The case they’d gotten into was wild and amazing and fantastic, but it was also unbelievably dangerous. They could be possibly facing an entire alien invasion, and it was just the four of them – seven now that Lanie, Esposito, and Ryan were in on it – against these terrible odds. As thrilling as that was, it was also probably the most dangerous case he’d ever been involved in. He’d choose to help solve this case no matter the danger, but there was no way he was letting his daughter get swept up in all this. He couldn’t tell her the most amazing thing he’d ever learned.

He only hoped his silence wouldn’t put her in more danger.

**Notes for the Chapter:**

> Have some Castle, Beckett, and River POVs all thrown in together. As for the Doctor's POV, that's a challenge I'm not sure I'm ready to tackle, so don't assume it's going to show up at any point in this story.
> 
> If River seems at all off, I'm really sorry. I haven't seen an episode with River in a while, and it's hard to write her in some of these more domestic situations. She's usually there right in the thick of the action, not sitting off to the side with the victims.
> 
> More soon, and there'll be more Esposito, Ryan, and Lanie.


	9. The Odd Sock

**Summary for the Chapter:**

> The team discovers a new lead - but something's not right.

When Castle got to the precinct with coffees in tow, he found Beckett sitting at her desk, completely focused on her computer, River lounging on a chair behind her. The detective looked up with a grateful smile as Castle handed her the coffee. “Thanks.” Castle noticed that River’s knowing smirk grew as she witnessed the exchange.

Beckett finished off what she was typing and stood. “We’re meeting in the morgue,” she told Castle quietly. He understood what she was saying; they needed somewhere to theorize where they wouldn’t be overheard, and the morgue would provide that. With a nod he followed Beckett and River to the elevator.

As the elevator doors closed behind them, Castle asked his partner quietly, “What are we telling Gates?”

In the same quiet voice Beckett answered, “That we’ve brought in Detective Cage and Dr. John Smith to consult and we’re hitting dead ends. She’s not happy, but it’s giving us room to work until we solve it.”

The partners shared a long glance as each wondered the same thing. _Once the case is solved, will there be someone we can arrest, or an invasion to stop?_

SCENEBREAK

Esposito, Ryan, and the Doctor were already there and working when Castle, Beckett, and River arrived. Beckett slung her jacket over a chair, frowning slightly when she took in the sight of the morgue. “Where’s Lanie?” she asked the detectives.

“Bathroom,” Ryan answered, not looking up from the laptop he, Esposito, and the Doctor were looking at. The Time Lord was seated in front of it, typing things in rapidly and scanning with his sonic screwdriver.

Esposito said in a gruffly awed tone, “We’re scanning through files of anyone who’s been brought in for arrest in the last three days. Dude’s fast with computers.” He cast a quick glance at the Doctor, who was dead focused on his work. “Still haven’t found anything though.”

Just then, Lanie came back in, eyes narrowed when she noticed the newcomers. “Hey Beckett, can you keep your alien here on a leash? I don’t need him trying to touch everything in this lab.” She shot Castle a glare and added, “He’s worse than you!”

Beckett rolled her eyes, but River appeared to be biting back a chuckle. “What did you do this time, sweetie?” She asked with amusement.

Without looking up the Doctor answered a little sulkily, “I was just looking.”

Lanie’s glare shifted to River, though it was more exasperated by this point than angry. “Can you keep your boyfriend here from messing up any of my equipment please?”

River laughed, seating herself in one of the chairs that had been set up. “It’s husband, actually,” she said with a smirk at Lanie, Beckett, and Castle’s surprised expressions, “and I can’t promise anything. For a thousand-year-old Time Lord, he can act like such a child sometimes.”

The medical examiner replied drily, “Sounds like someone I know.” She shot Castle another quick glare before getting a seat herself. “So what are we doing exactly?”

“Looking for anyone with a file and identity that’s been faked with alien technology,” Ryan answered, still sounding slightly shocked at what he was saying. “The Doctor’s looking through files while we try to figure out what’s the most logical thing the alien would have done.”

Lanie nodded thoughtfully. “Well whatever your killer is, he’d have to worry about hiding the murder weapon,” she pointed out.

“Tanya said it’s a sword,” River recalled, “So it’d be pretty big and bulky.”

“Something like that wouldn’t be easy to discard, it’d be too noticeable,” Castle added. “Big shiny sword, glowing from the heat. If the Fatorin left the scene quickly like we thought, he couldn’t have had time to find a proper hiding place for it. He must have taken it with him.”

Beckett nodded thoughtfully. “So if he took it with him, he’d have to keep it hidden and keep out of sight. A sword isn’t something you can just hide under your coat. So he’d have to stay where people couldn’t see him.”

“Unless he had a car,” Ryan pointed out, causing Beckett to groan with frustration. That put them right back to square one.

“Wait a minute,” Castle said slowly. “A car. What if he had a car?”

Beckett shot her partner a confused side glance. “We just said that Castle.”

“No, I mean it. What if he had a car? If he did, he would have had to steal it.” He hurried over to the computer the detectives and the Doctor were huddled around. “You guys were looking at security footage right outside the garage, right?”

Esposito nodded, understanding suddenly flashing in his eyes. “If it’s stolen, we can see if the plates match with a car that was reported missing,” he realized aloud.

The Doctor minimized the files he was reading and pulled up the security footage. He fast forwarded through the footage, only pausing occasionally at a screen-shot on the plates of each car passing through. On a separate application he used his sonic screwdriver to scan through stolen car reports with dizzying speed. After few minutes, he paused the footage, snapping the head of the screwdriver back into place. “And there it is!” He pulled up the last file he'd been looking at. “A stolen red Honda Civic with plates (make up plates).” He pointed at the paused footage, where the first few numbers of the plates could be made out. “That's the one.”

“Nice find,” Beckett said, coming to stand behind the laptop as well. “Alright Doctor, see if you can track it's progress with traffic cams and find out where it went.”

The Doctor nodded confidently. “I'll have an address in a few minutes,” he promised with a smug grin.

River rolled her eyes. “You think you're so clever.”

“Yeah, and so do you,” the Doctor fired back with a cheeky grin.

River shook her head. “I hate you sometimes.” 

The Doctor just chuckled. “No you don't.”

Beckett looked from spouse to spouse for a moment before shaking her head and moving on. “Once we have an address, we'll all head over.” She paused as she noticed how Castle, Esposito, and Ryan were staring in awe at the laptop and the Doctor. “What is it?”

Without moving his gaze, Castle asked in an awed tone, “Can we get one of those?” He pointed at the sonic screwdriver with reverence. Beside him Esposito and Ryan nodded fervently.

Beckett shared an exasperated look with River and Lanie. _Boys and their toys._ Aloud she just said, “Just let the Doctor work, guys.”

SCENEBREAK

A few hours later saw them pulling up to an abandoned warehouse not far outside the city. The area around it was fairly barren, giving the warehouse a wholly deserted feel. A perfect hiding place for an alien far from home.

Beckett shared a wary glance with Ryan and Esposito as they all headed quietly towards the building. All three cops and River were armed, but with only four guns against unknown odds, Beckett didn't like their chances. But they had no choice.

The door was locked, but the sonic screwdriver quickly fixed that. Silently the cops filed into the building, followed first by River, then by the unarmed Doctor and Castle. The Doctor still seemed a little put out that they had brought guns with them, but as Beckett had pointed out, the alien had already murdered someone and was likely to be dangerous. He seemed to have only relented about the guns because Beckett, Ryan, and Esposito were trained cops who would only shoot as a last resort.

The warehouse was filled with empty shelves and various clutter, but that couldn't disguise the fact that there was no alien to be seen. Gun still at the ready, Beckett headed further into the room, hoping to catch some sign of movement. But there was nothing. She deflated in disappointment. No one was in there but them.

“Beckett.” The detective looked up to see Esposito motioning her over. When she came closer she saw a trapdoor near the corner, which looked like it led to a basement, probably once for storage. Hope restored, Beckett motioned for the Doctor to unlock it. The Time Lord obliged, and they quietly swung the trapdoor open to reveal a short ladder leading to a room below. The trapdoor fell against the ground with a clatter, and Beckett knew that wouldn't go unheard. If they wanted to keep the element of surprise, they had to act now.

Beckett jumped quickly down into the room, landed on her feet, and straightened immediately with her gun held up. “NYPD! Don't move!” Esposito and Ryan were quick to join her, but she didn't notice them. All she saw was the huddled shape on the floor. Cautiously, she and the other detectives approached, in case it was hiding a gun, but the creature looked to be in no shape to fight. It was the brown-skinned, cow-eared Fatorin they'd been chasing, but it seemed to be asleep, and wounded. Blood stained the strange leather suit it wore, seeping through and creating a puddle around it. Its face was bruised and scratched, and it appeared to be whimpering in its sleep.

Castle's voice sounded behind her. “What happened to it?” She turned to see that he and the Doctor were now behind the four gun-wielders, Castle looking confused, the Doctor looking concerned.

At the sound of Castle's voice, the creature jerked awake, wincing in pain at the sudden movement. It looked around with wide yellow eyes that held both fear and hatred. “Who are you?” the creature hissed. Its voice was British and male, with a deep, guttural sound to it.

In a calm tone, Beckett replied, “We're the police. What is your name?”

The alien glared distrustingly at her before lowering his head a little. “Crah,” he finally answered. “Crah Rotir Sta.”

Beckett nodded. “Alright Crah. We're here about the murder of the Arondrian Tikrah. Would you know anything about that?”

Crah blinked a few times before letting out a throaty, painful laugh. “Of course I do, I killed him after all.” He spat out blood, eyes screwed tight with pain.

The detective blinked in surprise. That had been an easy confession – something was off. “Why are you admitting to it? Is murder not illegal where you're from?” She asked drily.

The alien laughed again, a hand clutching his ribs painfully. “Because it was necessary. There is nothing you can do to stop us now.” Crah's eyes took on a feverish look, and he began speaking more rapidly. “When the Arondrians ran, we followed. We came with ships and guns and battle, and we will stay until this world is ours. All of it ours – for Raktor.” He spat out more blood and began chuckling, an eerie, hollow sound. “I was seperated. Hunted the Arondrian, silenced him. He could not warn this world. Must not tell them what he had seen. What we had done. He fought back. Was strong. Used blade against me.” The creature flashed a toothy, vicious smile. “I won.”

The alien's feverish rambling sent a tremble through Beckett. The detective's breath caught in her throat. “How many of you are there?” she asked hoarsely.

“Many. So many.” Crah seemed delirious now, a breathless chuckle forcing its way through his pain-clenched teeth. “So many tyron weapons. We will wipe you out of the sky. For Rakto-” The alien broke off for a moment, eyes bugging wildly. Then he let out an ear-piercing shriek, every limb going stiff, his back arching in agony. The humans hurried to help, but beyond pinning down his limbs so he wouldn't thrash and hurt himself, there wasn't much they could do.

The Fatorin gave a few spasms, then slumped against the ground, his crazed, feverish eyes becoming blank. Beckett blinked in shock, unable to comprehend what had just happened. Only a few seconds had passed, but Crah was dead.

Their killer was dead, but there was an entire invasion force to be reckoned with, and they had no idea how to prepare for it.

SCENEBREAK

They had gathered back in the top floor of the warehouse. It was too uncomfortable speaking near Crah's body, which they'd agreed to bury before they left. River could tell this didn't sit well with the detectives, but there wasn't any logical way of reporting this death, so they had no choice.

The four humans seemed very shaken by what had just happened. They sat close together, eyes shadowed, clearly trying to come to terms with the combined threat of invasion and watching Crah die so horribly in front of them. River herself was having trouble pushing images of the dying Fatorin out of her mind, but beyond that all she felt was anticipation. Finally, the waiting and sitting was over. The world was in danger again, and the mad chase to save it would be picked up. Another invasion to stop, another threat to face, all in a day's work.

Beside her, she could see the Doctor was similarly determined, though perhaps not as excited as his wife. He never responded well to death, even the death of a psychotic murdering Fatorin. Still, there was a certain air of anticipation about him as well. Now, finally, they were in their element. Saving the world was what they did.

“We need to find the rest of the Fatorins.” That had been Beckett. The detective looked slightly pale, but determined.

“Oh, that's easy,” the Doctor said absentmindedly.

Beckett jerked her head around to look at the Doctor. “Easy? What do you mean?”

The Doctor held up his sonic screwdriver in response. “This thing's been reading tyron energy like mad ever since we got in here,” he explained. “I've got enough of a sample that I can trace it back to it's source, easy.”

Esposito frowned thoughtfully. “So we just follow that energy thing and find the aliens, just like that?”

The Time Lord nodded. “Yeah, why?”

No one spoke for a few moments. Then, to River's surprise, Castle spoke up. “No. There's no way. It's been way too easy.”

River's brow furrowed. “What do you mean?”

The writer stood, too full of nervous energy to stay seated. “All of this. Finding the tyron energy in the garage – I mean, it's not like the sword was shedding it everywhere they went, otherwise we would have found a trail, so what was so much of it doing at the garage? And why is there enough here to lead you back to the source? There's no reason for it.”

Beckett seemed to pick up on her partner's train of thought, snapping out of her momentary funk. “And Crah. He was really badly wounded, which suggests he was in a fight.”

“But Tikrah only had the one wound on his throat, which means he was taken by surprise and killed quickly,” Castle explained.

“Tikrah wasn't a strong man even wearing a human shimmer, he couldn't have wounded Crah that badly.”

Esposito and Ryan had listened thoughtfully, and now both were nodding. “There was something up with Crah too,” Esposito pointed out. “He almost looked drugged or something.”

“And he was way too eager to tell us about their invasion,” Ryan added. “If he killed Tikrah to keep him from warning people, why tell us at all?”

River looked at the four humans in surprise. She and the Doctor had been so caught up in the idea of saving the world again and throwing themselves into the adventure head-first had kept them from really looking at the facts. The Doctor had rather an act first, ask questions later policy, but here these humans were, stepping back and actually thinking and planning things through. She wondered a little enviously what it might be like to actually have a plan for once.

The Doctor too seemed interested in the humans' theories. “So why do you think they're making it easy for us?” He asked curiously.

“Because it's a trap.” The words were out before River had fully finished the thought. When the others turned to look at her, she explained, “They've basically laid out a trail for you to follow. They've probably got some sort of trap waiting.”

“Yeah, but a trap for who?” Esposito asked.

River turned to her husband. Solemnly she told him, “I think it's for you, my love.”

The Doctor blinked in surprise. “Me?” Then he thought about it for a few moments, his expression hardening. “I'm the only one with the technology to track it,” he realized grimly.

The archaeologist nodded. “You have to admit the situation is rather tailored to you. Innocents hurt, an invasion to stop, Earth to save. How could you have ever resisted?”

The Time Lord's eyes hardened for a moment. “Once – just once – I wish my enemies wouldn't get it in their heads to go after Earth first.” River knew some of the horrible fights he must be remembering, and her heart ached for him, but right now they needed to focus on the case.

Esposito spoke up again. “So if we follow that energy trail we're walking into a trap?”

River nodded. “We can assume.”

“Then let's not walk into it.” Everyone turned to see Beckett standing beside Castle, arms crossed determinedly across her chest. “Whoever's setting this trap, they're setting it for the Doctor, not us. They might not know about us.”

The Doctor frowned. “What are you suggesting?”

“You go in first to get their attention, then we stay hidden and be your back-up,” Beckett explained. “If you get in trouble we can get you out, but it'll be easier if they don't know we're there.”

The Time Lord looked thoughtful for a few moments, then narrowed his eyes slightly. “Alright. But River's in charge.”

The woman in question let out a snort. “Fat chance,” she told her husband. “I'm staying with you. The Doctor always travels with a companion, remember? Anyone who's ever fought you knows that. It'd be a bit suspicious if you went in there alone.”

The Doctor turned to his wife with an unusually serious expression. River faltered slightly at his unusually intense stare. “River, this is important,” he chided gently. “You're the cleverest one besides me. If we need to dismantle some complicated alien technology, you'll be the only one besides me who'll know how to do it.” In a quieter voice, he added, “And you're the only one I trust to keep the guns under control.”

River felt a rush of warmth as the realized the depth of trust he was giving her. She had run with older Doctors before, true, ones that knew her even better, but this one loved and trusted her so much. It almost scared her to think what would happen when she lost that. She gave a grim nod. “Fine. But you still need a companion.”

With a smile, the Doctor turned to Beckett. With an offered hand he asked, “Would you be willing to play the part?”

The detective blinked in surprise. Some strange emotion flashed in her eyes; River wondered if she was thinking about the night before and what she'd told her about traveling with the Doctor. _Is she wondering what it would be like to actually be the Doctor's companion?_ she wondered thoughtfully.

After a few moments, Beckett accepted the outstretched hand. “Sure.”

They had a plan. River just hoped it didn't turn out like the Doctor's usual plans.

**Notes for the Chapter:**

> If there's anything completely wrong or just plain gross about the second half, I apologize. It's nearly midnight and I probably should've stopped attempting to write a few hours ago, but I'm currently in a sort of haze being fueled by the need to finish this chapter. Or something. Either way, my writing's usually crap after a certain hour, so again I apologize. I especially feel like shooting the whole bit with Crah - it's way too abrupt, too cliche, too blah, but whatever, my brain's not about to come up with anything better.
> 
> We're closing in on the end here. Only a few chapters left - two or three if I'm guessing right. I really hope you've liked this story so far and you'll like the way I finish it. I tried hard to come up with a good mystery and an equally good explanation, and I hope I succeeded. Keep an eye out for the next chapter, I might even get it done tomorrow. If school's out because of snow, which seems to be the idea, then definitely.
> 
> The title is a reference to the Nikki Heat series, which is an actual book series written by a ghost writer pretending to be Richard Castle. In the books they refer to a fact that stands out or doesn't add up as an odd sock - and there's quite a few of them here.


	10. Last of Their Kind

**Summary for the Chapter:**

> The team traces the source of the tyron energy.

They agreed to take the TARDIS to the source of the tyron energy. Luckily no one was in Castle's flat when they got there, so they were able to watch as the Doctor slipped into the invisible TARDIS without any awkward questions from Castle's family.

A few moments after the Doctor had closed the door behind him, the blue police box materialized into view once more. Castle grinned at the sight of it, as did the Doctor once he came back out to join them, but Esposito and Ryan looked less than impressed. "That's your spaceship?" Ryan asked doubtfully.

"You couldn't fit three of us in there," Esposito objected.

The Doctor just smirked. With a snap of his fingers, the doors swung open, and he gestured toward them with a flourish. "Go and see for yourself."

Exchanging a baffled look, the partners approached the box. Castle and Beckett followed, both wearing a smug look. Now it was someone else's turn to be wowed by the TARDIS.

Their reaction when they walked in was priceless. Esposito stopped dead, and Ryan let out a low "Whoa," under his breath. Both looked around the console with wide eyes, trying to take in the amazing sight. Ryan's mouth opened and closed a few times before he finally managed a weak, "Well... I wasn't expecting that."

"It's huge!" Esposito breathed, blinking wildly, as though convinced the TARDIS would grow smaller again in the blink of an eye.

Castle came up behind the partners, slinging arm arm over each of their shoulders. "Gentlemen," he said with a grin, "welcome on the TARDIS." He held back a chuckle at their awed expressions.

"Right." They turned to see the Doctor hurrying through the door and to the console. He dashed around the console, throwing up switches and pulling levers, the familiar manic grin on his face. "I'll land us a few hundred feet from the source of the Tyron energy. You four can pop out and find a way to follow us while Beckett and I take the TARDIS straight in."

Memories of his last flight in the time machine came to mind, and Castle turned to the detectives. "Word of warning, it's a bit of a bumpy ride."

"That's because he doesn't drive her properly," River spoke up from by the door. "She has stabilizers for a reason, sweetie."

The Doctor threw a quick scowl in her direction. "They're boringers!" He complained. "They're just big blue boringers." River just sighed affectionately in response.

Castle left the partners behind and crossed over to where Beckett stood leaning against the railing. "I wish I was going in there with you," he said quietly. He hated seeing her go off into danger without him, even though she was the more experienced of the two. He also wished that he'd had have his partner by his side while they wandered into the unknown, shadowy den, but she needed to be at the Doctor's side, and he had to be her back-up.

Beckett seemed to understand. She gave him a quick, warm smile. "I know. But we'll be fine. And I need you to keep an eye on the boys."

Castle just nodded. He didn't voice his other fear; that the Doctor might make a better partner than him. It wasn't even a real fear. The writer had grown beyond actually worrying about being replaced. He knew that he and Beckett were partners and that was that, but he couldn't help that little irrational worry that somehow the Doctor, with his time travel and his crazy stories and his journeys to the stars, might take his place.

There must have been some hint of it in his face, for Beckett's expression softened into a warm smile. Castle went to pull her into a hug, but Beckett surprised him by pulling him into a long, proper kiss, regardless of Esposito, River, and Ryan's smirks and the Doctor's mix of amusement and disgust.

When they pulled back, Beckett was grinning at him. "I'll come back," she promised simply. And Castle believed her.

This time Castle was prepared for the massive shudder that ran through the ship. He and Beckett were already holding on to the railing, but to his amusement Ryan and Esposito were thrown off their feet. The ship jostled around for a while before jerking to a halt, again lacking the _vworpp, vworpp_ that it had given the first time they'd seen it.

The Doctor threw down a final switch. "Right then, here we are, right outside the lion's den." He gave his monitor a quick look. "Hmm, 'den' looks about right. It's some sort of cave."

The humans crowded around to get a look at the monitor. It looked like a very foresty area with a large cliff face. A wide, gaping cave mouth was cut into the rock. Castle's eyebrows flew up at the sight. "Well that's probably the most stereotypical evil lair I've ever seen."

The Doctor hurried to the door. "Alright, everybody out, let's get going."

Esposito, Ryan, and River headed out the door, but Beckett held her partner back for a moment. "Here," she said as she pushed her gun into his hands. "I get the feeling the Doctor won't want me to have it anyway. Be careful." Castle nodded and gave Beckett one last smile before following them.

She'd be fine. He'd make sure of it.

SCENEBREAK

Beckett watched as her partner and the others exited the TARDIS. Now that she was alone with the Time Lord and his machine, she felt a sliver of self-doubt. They had no idea what they were about to walk into. It could be anything. What if they already knew who the Doctor's companions were? What if they were found out?

The Doctor's voice broke the detective out of her thoughts. "So, we've got an unknown beastie trying to lure me into a secret cave with unknown intentions?" His grin widened as he began to work on the console again. "Let's go and poke it with a stick."

Beckett forced a grin at this display of enthusiasm, so like Castle. But he wasn't her partner, and Beckett couldn't help wishing that the writer was going into this with her. They weren't just dating, they were partners. They watched each others' backs and trusted each other implicitly. She wished that she was walking into this unknown danger with the man she trusted with her life, but instead she got the Doctor.

But Castle would still be there, waiting in the shadows to be her back-up, and she knew that as long as they were both there they'd both be safe. Because there was no way she was letting anything happen to him either.

The Doctor seemed to notice her silence. "Are you alright?" He asked with concern. There was nothing condescending in his tone, just genuine concern.

Beckett straightened, looking the Doctor dead in the eyes. "I'm fine," she told him confidently. "Let's go get this son of a bitch." The concerned girlfriend was gone, leaving the cool, savvy detective in her place.

The Doctor's grin returned full force. "Extrordinary Kate Beckett. The aliens don't know what's coming for them." He raced over to the console to throw up one final switch, sending the TARDIS back into violent shudders. "Geronimo!"

SCENEBREAK

When they stepped out of the TARDIS, they found that they were fairly deep inside the cave. A hole in the roof far over their heads had sent sunlight spilling into the cave like a spotlight, with the edges of the cave still consumed in shadows. There was no alien in sight, but as they closed the door of the blue box behind them, a sharp hiss sounded out of the shadows. " _Welcome, Doctor, and your human companion. I've been expecting you two._ "

Beckett tensed in anticipation, but the Doctor just gave an easy grin, bouncing forward on the balls of his feet. "Well hello there. You must be friends with Crah."

" _The Fatorin was merely a puppet, Time Lord. It is you I have waited to meet._ "

The Doctor stared cooly into the shadows, a slight smirk on his face. "So you manipulated a Fatorin into killing his enemy, an innocent Arondrian, then somehow tricked him into thinking it was his idea before killing him? And all to get my attention?" He paused, waiting for a confirmation that didn't come, before saying, "It's a brilliant set-up, I'll give you that. So can we maybe meet the person pulling the strings?" A long hiss followed his words, spewing ominously out of the darkness.

A sleek black form slithered out of the shadows. It was like an enourmous snake, with smooth black skin like blubber, and a rounded head with a tapering snout. Cold ice-blue eyes blined out at him from that face, with long, thick whiskers sprouting from his jaws. The tip of his tail had similar, even thicker whiskers, more like feelers or antenae, which waved lazily in the air. His body was thick as a person is wide, and from his snout to his tail he could have been as long as three busses.

At the moment, his neck was raised so his head was lifted high over their heads, swaying slightly as his gaze fixed on the Doctor. When he spoke, it was in a voice like steam escaping, a long, drawn-out hiss. “ _Welcome, Time Lord._ ”

The Doctor gaped up at the creature. “You're a wyvern,” he breathed. “But that's impossible.

The creature didn't seem to need to blink. Those eyes stayed fixed on the Time Lord with eiirie intensity. “ _No more impossible than you, Doctor. The last of the Time Lords._ ” Those icy orbs narrowed slightly. “ _Yes, the very last of your kind. A common title these days so I'm told, and one that I share. I am Torkk, last of the Wyverns._ ” Malice flooded into his expression as his voice dropped to a low rumble. “ _Thanks to you._

Beckett threw the Doctor a worried glance. “What does he mean, Doctor?”

The Doctor didn't take his eyes off the wyvern as he explained, “The wyverns lived on a planet in the same system as mine, as Gallifrey. They were a hunter-tribe race, didn't have advanced much in technology, but inherently telepathic. They had the ability to influence the minds of others through touch, like Time Lords, but so much more advanced.” His eyes shone with a balance of admiration and distaste. “One touch and they could slip right into your mind and leave you thinking you're a pink flamingo with an umbrella for the rest of your life.” His brow furrowed slightly. "Though you must be out of practice. Crah didn't take the false memories too well, fried his brain clean out."

Torkk let out a vicious hiss at the Time Lord's insinuations. “ _We did not use our powers for ill!_ it screeched, thrashing his tail furiously. “ _We were not conquerers or manipulators. We used our skills to hunt enough prey to feed our many mouths. We were a large people, and our prey was vicious as we. It is no different than the snake paralyzing its victim with venom. We used our powers to survive!_ ”

Sadness flashed in the Time Lord's eyes as he countinued his narrative. “My people always knew about the wyverns, but we never interfered until the Time War...” he trailed off, his expression becoming one of infinite sadness. Beckett had not believed until now that he was over a milenium old, but now she could see every year on his shoulders like a weight.

Torkk let out a menacing hiss. “ _What? Will you not tell her, Time Lord?_ ” He lowered his head and neck to the ground and began circling slowly around the four. “ _Tell your precious companion how your people enslaved mine. How they created great machines to enslave us, to cut us off from our telepathy, leaving us helpess. How your people stole our minds and left us dumb as beasts, then set us loose against your enemies like common creatures of war._ ” Something shook in his voice, like the sound of a rattlesnake. “ _My people were a peaceful race, and the Time Lords enslaved us!_ ” He circled more furiously around the two, no longer speaking, just letting out a long, furious hiss.

The Doctor watched the wyvern with horror and pity. “I'm sorry,” he said softly, “I am so, so sorry.”

The wyvern stiffened, pausing in his manic circling, then turned a hateful, blazing glare on the Time Lord. “ _And you, Doctor. The worst of them all. We thought you pitied us, Doctor. Those of us too young to use for war, those with our minds left. We saw you and thought you were our savior. You were different from the others. We thought you cared._ ”

He drew his head closer to the Doctor, ice-blue eyes still unblinking. “ _Then you murdered us! You destroyed the wyverns! Gallifrey burned, and we burned with it! You came in with your morals and your rules and you burned your own planet to the ground. You didn't save anyone! My people are dead because of you!_ ” He roared out the last words in the Doctor's face, his whiskers waving uncontrollably.

Beckett froze in shock. _He_ had killed the Time Lords? His own species? She remembered how completely broken the alien had seemed that night he had told her that his planet had burned, and she had felt a connection. She'd felt _sorry_ for him. She'd thought they were the same, grieving over something that was taken from them. But he had been the one to pull the trigger. She turned to him, looking the broken Time Lord right in the eyes. "Is it true?" She asked in a low, dangerous voice.

The Doctor flinched. “I had to,” he whispered hoarsely. Beckett felt like she'd been punched. She'd felt sorry for him, she'd thought they were both victims. But he was the murderer. “The Daleks were too powerful, and my people...” his voice went dry, and he had to swallow before continuing. “My people had grown destructive to an unstoppable level. They were going to destroy the entire universe and everything in them. They couldn't be reasoned with. I had to stop them. It was my planet or the entire universe.” He looked the wyvern in the eyes as he whispered, “I am truly sorry.”

Torkk's hissing subsided, his eyes boring into the Doctor's. “ _I know. I know you feel guilt, believe me. I know you repent every day for the havoc you have wreaked. And believe me when I say,_ ” here he leaned in even closer, “ _that it is not nearly enough.”_

The Doctor looked with infinite sadness at the wyvern. "You lost your entire species, and you rage at me for harming innocents," he said quietly, "yet you murder an innocent and fry a Fatorin's brain just to get my attention."

The hissing reached a higher pitch. " _I did what was necessary to draw you out of hiding,_ " Torkk spat viciously. " _I used a Dalek metal transport beast to escape before the Time War ended. I wandered a long, long time trying to find you, Doctor. When I landed on Akali, they told me that the last Arondrians had fled to Earth. That's when I knew I had you. I stole a Fatorin and forced him to point me to Earth. I knew that the harming of alien innocents on Earth would be the perfect bait for you._ "

The Doctor shook his head sadly. "Murder is never necessary," he said gently. "You should know that better than anyone. But here you are, the righteous defender, with innocent blood on your hands. Friedrich Nietzsche saw that once. 'He who fights with monsters might take care lest he thereby become a monster.'" He let out a sigh. "Look what you've become, Torkk."

There was no regret in the wyvern's eyes as he hissed, " _Do you think I care? All I want is to see you suffer, Doctor. And I plan to._ "

His tail tip snaked out and touched the Doctor's forehead, resting there. The Doctor stiffened, his eyes widening. Torkk let out a fierce hiss. “ _I can see your mind, Doctor! Oh, a difficult mind to be sure, harder to break. The great Time Lord mind, enough to hold galaxies. And as you say, I am out of practice. This will take time. But no matter, no matter. For I have seen your soul, Doctor, and I know just how to break it. Shall I show you?_ ”

The Doctor's body went completely rigid, his mouth opening in a silent scream of agony. Torkk let out a delighted hiss. “ _Yes, Doctor! Feel it! Every life you've ever stolen. Every dark act you've committed. Every lie._ ” The creature leaned in closer, hungrily taking in the sight of the Doctor's agony. “ _I can see them all, Doctor, can you? The Time Lords, the Racnoss, the autons. Daleks, cybermen, silence, sontarons, the list has no end. What a legacy you leave, Doctor._ ”

The Doctor crumpled, falling onto his knees, his hands covering his face. The wyvern let out a cruel screech of laughter. “ _'The Doctor.' The man who fixes people. The wise man, the healer. Even your name is a lie. Shall I tell you your true name? The Oncoming Storm. The Destroyer of Worlds. The Predator. You are the man who destroys everyone, even his friends._ ” The creature's gaze shifted briefly to the horror-struck detective. “ _You surround yourself with humans, Doctor, and you cut even their tiny lives short. Every human who has followed you has been lost. Sarah Jane, Martha, poor lost Donna. Even the pretty blonde, the girl who foolishly forgave you for the Time War._ ”

The Doctor let out an agonized moan. “Rose...”

Torkk shrieked gleefully. “ _You lead your companions like lambs to the slaughter, and you do it again and again! Feel it, Doctor! Their fear! Their pain! Their blame! For you, Time Lord, are the reason for their suffering. Feel it all, Doctor, and remember the wyverns!_ ”

Beckett watched the Doctor's agony uncertainly. A small part of her brain wondered if maybe this was the Doctor deserved. The murderer of an entire planet and more than one race. The choice had faced had been a hard one, yes, but as hard as she tried, she couldn't imagine being the one to pull the trigger on her mother, no matter the price. It was too deep a pain. How could the Doctor live with what he'd done?

But at the same time she knew that the Doctor really was trying to help, and no matter what he'd done, she couldn't let him die. It was her job as a cop to protect him. But without a gun, there was nothing she could do. She was too small compared to him, and she couldn't ask the Doctor what his vulnerabilities might be.

_Where are you Castle?_ she wondered desperately. _I could use one of your theories right now._

SCENEBREAK

Castle had followed River and the detectives into the darkness of the cave. They had filed silently through the darkness, each wondering what they were going to face, until they'd reached a wide cavern. There were some higher ledges where they could oversee what was going on, so they clambered up as silently as they could and waited for the TARDIS to arrive.

As the TARDIS arrived and the scene unfolded before them, Castle watched the wyvern with interest. This wasn't a conquerer here to invade. This was a victim fueled by anger and revenge. Somehow, that made him seem infinitely more dangerous. A cornered animal was more unpredictable than a calculating hunter.

The creature's accusations shocked Castle as well as his partner, but the Doctor's explanation held a ring of truth. His own people or the universe. What a terrible choice to face. He could understand why the Time Lord had made his choice, but he knew Beckett might not. After the way she lost her mother, she might not be able to accept what the Doctor had been forced to choose, and Castle got that.

But he also knew that she would do whatever it took to stop Torkk from killing the Doctor.

Esposito started to raise his gun, but River reached out and forced it down, shaking her head. "Kill him or wound him and the Doctor stays like this," she hissed in a low voice. Even in the darkness, Castle could hear her fear for her husband in her tone.

As he tried to think of a way to help, something from earlier in the conversation came to him. " _They had the ability to influence the minds of others through touch, like Time Lords, but so much more advanced.._ " He'd also said that the wyvern was out of practice. Maybe having too many memories forced on him would disorient him?

Castle reached out and put a hand on both detective's shoulders. "Do you trust me?" He asked in a low whisper.

Esposito and Ryan nodded immediately. River thought for a moments before giving a firm moment. Castle explained, "Then do what I do. When you do, remember as much as you possibly can. Remember everything."

Before they could ask him to explain that baffling statement, Castle was scrambling down from the ledge's and racing towards the wyvern. He could hear Beckett calling his name briefly before he reached out to touch the wyvern's vast side. Then his world exploded into pain.

Memories that were not his we're being forced into his head - memories of pain and vengeance from the wyvern, and memories of grief and guilt from the Doctor. The pain and death of millions. With a fierce effort he ignored them and called his own memories to the front of his mind. Growing up with Martha, becoming famous, Meredith, Gina, the birth of Alexis, raising his daughter, the first time he met Beckett. All the pain and sympathy he'd felt for all the murder victims, all the families. The love he felt for his family, and for Beckett. He pulled up all of his strongest thoughts and emotions and pushed them at the wyvern.

" _What are you doing?!?_ " the wyvern hissed furiously. Castle didn't answer, just focused on his memories. He heard footsteps as the rest of the team raced over, and he felt the surge of new memories as the three detectives and River touched the wyvern.

Case after case from Ryan and Esposito, the grim sadness of working with death. From River he felt the terror and training of her early life, then the confusion and love of meeting the Doctor, the dizzying fear of one day losing him. The Doctor's guilt was easiest thing to feel. The guilt of a million deaths, all huddled on his shoulders, and he thought he deserved it all. That pain screamed out through their telepathic connection, but Castle ignored it and focused on Beckett. He could feel the agony of losing her mother, the mask of being okay, the way her life slowly pieced together again. And he felt her love. Her love for him sang through his mind, and he focused on that, tried to block out everything else, to keep his mind from going insane with all the voices in it.

Suddenly, the Doctor grew stronger in all their minds, then the connection was severed. As the fog of memories cleared from Castle's vision he could see Torkk slither back as though he had been struck. His ice-blue eyes were wide and crazed, his tail thrashing wildly. " _What have you done?!?_ "

"I changed you." The grim answer came from the Doctor. The Time Lord still looked deathly pale, and he had to lean against River to stand, but his expression was one of grim judgement. "Your abilities aren't as strong as they once were. While they distracted and overwhelmed you, I went into your mind and locked your telepathic abilities inside your mind. You won't be able to reach inside anyone else's mind ever again."

The wyvern thrashed his head furiously from side to side, an ear-piercing shriek issuing from him. " _You took my protection!_ "

The Doctor shook his head. "I took your weapon," he amended gently. He took a step towards the wyvern, his gaze imploring the alien to see reason. "Now let me help you, Torkk. There's been enough loss already. You're right, the death of the wyverns is my fault, but I'm not about to finish that genocide. I can find you somewhere safe to live. Please, Torkk. Let me help you."

The wyvern shook his head violently, his glare fixing on the Doctor once more. " _There is nothing left for me, Doctor. All I have left is destroying you._ " He lunged at the Time Lord with teeth bared.

Four gunshots rang out. Castle couldn't have said which one of them had hit their target, but the creature jerked back with a sudden scream, then collapsed against the ground, his thrashing growing steadily weaker.

The Doctor looked stricken, but he didn't turn to yell at anyone about the use of guns. Instead he knelt by the wyvern's head, eyes heavy with sorrow. "I'm sorry," he said quietly. "I am so sorry."

Torkk blinked back at the Time Lord, hatred burning in those icy blue orbs. " _Remember this, Doctor. You are responsible,_ " he rasped, blood gurgling in the back of his throat. " _Another genocide to add to your glowing legacy. You murdered me, Doctor. You killed the last of the wyverns. My blood... is on your... hands..._ "

The creature's eyes rolled to the back of his head, and his head fell to the ground with a dull _thump_. He let out a few last, shaky breaths before stilling, his eyes becoming glassy and dull. The last of the wyverns was dead.

No one spoke for a long time. Without a word River came to stand beside the Doctor, wrapping her arms around him from behind in a silent hug. Castle and Beckett exchanged a solemn glance before joining River by the Doctor's side, soon joined by Esposito and Ryan. Silently, the small team stood huddled together, joined in the memories they had just shared, yet each wrapped in individual grief. They stood in mournful silence over the last of the wyverns, and wondered at what their victory had cost.

**Notes for the Chapter:**

> So here we are at the end. There's going to be one last chapter to wrap up loose ends, but the mystery is solved, and the culprit dead. I hope you've liked how the mystery turned out and how everything was wrapped up.


	11. Goodbyes

**Summary for the Chapter:**

> The Karrows learn the truth and goodbyes are said.

The trip back to Castle's flat in the TARDIS was a solemn one. No one spoke as the ship shuddered to a halt. Esposito, Ryan, and River quickly exited the ship, but Beckett lingered for a minute. Castle watched curiously as she came to stand beside the Doctor, who was staring down at the console, his gaze dark.

The detective stood with him in silence for several moments before speaking up quietly. "Even after what he did to you, you gave him a chance." It wasn't a question, but it seemed to require an answer anyway.

"Yeah," was all the Doctor said. They stood in silence after that, but Castle could see that Beckett had chosen to forgive him for the destruction of the Time Lords. In their attack on the wyvern, they had felt the memories and emotions of the entire team, and the depth of guilt the Doctor felt over his many atrocities had been there for all of them to see. Apparently it had been enough to convince Beckett that the Doctor really hadn't had a choice, that it wasn't his fault.

The detective laid a comforting hand on the Time Lord's shoulder. He looked up at her, eyes wide with surprise and the faintest hint of hope. Beckett gave him a small smile, her hand still fork on his shoulder. After a moment's hesitation, the Doctor gave a brief nod of thanks. They stayed like that for a few moments, then Beckett drew back and rejoined Castle, following him out of the TARDIS.

Their job wasn't over yet.

SCENEBREAK

Esposito and Ryan had opted to go home instead, since they weren't leading the investigation, so it was only Castle, Beckett, River, and the Doctor who arrived via TARDIS in front of the Karrow's apartment building. The Doctor didn't hesitate at all when they finally knocked on the Karrow's door, but Beckett could see shame in every line of his face. _He really cares,_ she thought with slight surprise. _After all the death he's seen, so many lives lost, and he still cares about this one life._

Tanya took the news surprisingly well. She was rather angry that her father had been killed because of something he had no control over, but she seemed to realize the Doctor wasn't the one to blame. "We're the last of our kind too, and you don't see us going after the Fatorins. The wyvern made his choice." She fixed the Doctor with her intense silver gaze, this time with sympathy rather than hostility. "It wasn't your fault, Time Lord."

The Doctor looked surprised at Tanya's words, but didn't respond, only giving a half-hearted nod. Beckett could see the alien still blamed himself for what had happened. She shuddered at the memory of the terrible guilt that had radiated from all of the Doctor's memories. To live with that kind of guilt for so many years...

After Beckett finished telling Tanya what had happened, the teenage girl turned to her with a mix of apprehension and her old defiance. "What are you going to do now that the case is over? Send us to foster homes?"

Beckett shook her head. "Normally, yes, but I'm not sending three aliens and a human from the future to live with unsuspecting foster parents. It wouldn't be safe for you. So, if you're willing to fudge the records a little bit, I think you might be able to pass for a young twenty-one-year-old."

Tanya's eyes widened in shock. "Wait, seriously? You're willing to falsify records so I can look after my brothers?"

Beckett smiled and explained, "You've got a very unique situation, Tanya. I don't think Tikrah would want me to split up your family. You guys need each other." She suddenly grew serious. "It's not going to be easy, though. You're going to have to get a job and support three brothers. You'll never be able to go to college either."

Tanya let out a snort. "Like that matters. I'm from the 51st century, there's nothing that some 21st century college could tell me that I don't already know. I'll just fake myself a diploma and get myself a decent job. Maybe something with programming."

The detective turned to look at the boys, who were talking with Castle and River in the kitchen. "Will you stay in New York?"

Tanya shook her head. "Not if we're safe from the Fatorins."

"You are," the Doctor said quietly. "By now they've deposed Raktor and couldn't care less about any leftover Arondrians."

Tanya gave an easy smile, looking her age for the first time since they'd met her, rather than a girl forced to grow up too quickly. "Then we'll head out into the country. It's too noisy and crowded here. Out in the country we can grow gardens and live in peace. It won't be Akali, but we can make it home anyway. I'll teach the boys the Arondrian ways, and our culture will be remembered through them." She looked at Detective Beckett with a mixture of determination and sadness. "We won't let Akali be forgotten."

Beckett was surprised at the girl's level of maturity. Somehow, she knew this girl and her family were going to be fine. "Call me if you ever need anything," she told her.

"I will, and Detective? Thanks for actually caring." She looked a little embarrassed by what she was saying, but pushed on. "Most cops would've turned this over to higher authorities or tried to figure out more about us, but all you cared about was catching Tikrah's killer. So... thanks."

The detective felt a rush of warmth. This was why she did this job. To ease the suffering of those who'd lost someone, and to let them know that someone actually cared, that was why she put herself through all the death and loss. She gave the girl a warm smile. "It was my pleasure."

When they left that family behind, watching them leave from their doorway, she had a feeling she wouldn't ever be seeing that strange little family again. But she also knew that they were going to be just fine. Oh, it'd be hard for a bit, and Tanya would have to work hard to find a place in the 21st century, but she also knew she'd pull through for her brothers.

The Arondrians would find their home on Earth.

SCENEBREAK

They all came to a stop in front of the TARDIS. Beckett knew that this was to be goodbye. She had an idea to invite them to one last dinner, but somehow she knew the travelers wouldn't accept. It just wasn't their way. And she knew the Doctor wouldn't want to celebrate something that he so deeply considered to be his fault.

The Doctor leaned back against the TARDIS, looking at Beckett curiously. "What will you tell your precinct?" he asked.

The detective shrugged. "Well, there is a lot of gang activity in that area. I'll attribute it to random gang violence." The words held a certain irony. She had sworn when she’d decided to become a cop that she would never pass off that sentence on anyone, not after Detective Raglan had given it to her mother. She’d sworn she’d always dig deeper than that and find out exactly who was responsible. But this time, the ruling wasn’t to protect a killer; it was to protect the victims. The killer had been brought to justice this time, and the victim’s family had been given their closure.

River nodded thoughtfully. “You sure you won’t get in trouble for that?”

“Maybe a bit,” she said with a shrug. “But if Esposito and Ryan back me up, Gates’ll have to let it stand.” She looked between the two time travelers with interest. “What about you two? What’ll you do now?”

“Well, it’s back to Stormcage for me,” River said with a smirk. “I’m sure the guards will be wondering what’s been keeping me. I usually don’t escape for longer than a day.”

Beckett remembered that Stormcage was the future prison, but she knew better than to ask why River lived there. She trusted her, and that was enough. “And you, Doctor?”

He looked fondly over his shoulder at his big blue box. “Oh, same old life. Back to the TARDIS, seeing all the stars, all of time and space. Unless…”

Beckett’s brow furrowed. “Unless?”

The Doctor looked a little uncertain, wringing his hands awkwardly. “Unless… well, you could come with me? The two of you?” Beckett and Castle shared a dumbfounded glance as the Doctor continued, “The TARDIS and me, we could take you anywhere and everywhere. If you want.”

As Beckett tried to collect her thoughts, she heard Castle ask a little hoarsely, “Why us?”

The Doctor gave a little half-smile. “Because you two were brilliant,” he said simply. “Because you cared.”

The detective turned to her partner, her thoughts suddenly blazing with the images of distant worlds, past future, and all of it in their reach. They could go anywhere, do anything, help anyone. It was the offer of a lifetime. A dream beyond measure.

She looked at the man she loved, and she knew her answer.

Beckett turned back to the Doctor and told him gently, “We can’t.”

The Doctor deflated a little, so she explained, “We have family here, both of us. But it’s more than that. Our work, what we do, it’s important.” She straightened, looking the Doctor right in the eyes, imploring him to understand. “We help those who’ve lost family and friends. We speak for the dead, and we bring justice to those who have stolen lives. And that’s important. That matters.” She reached out for Castle’s hand and felt his fingers entwine with hers. With renewed confidence she told the alien, “We’re needed here, Doctor.”

The Doctor looked at both of them, still sad, but eyes warm with pride and admiration. “Kate Beckett and Richard Castle. Extraordinary Beckett and fantastic Castle. You’re brilliant, both of you.” He turned to look back at the TARDIS. “So this is goodbye then.”

Beckett nodded without regret. “Goodbye, Doctor.”

Castle added, “Come back and visit, alright? I want to hear more about outer space and time travel.”

The Doctor nodded, but it felt like a hollow promise. Beckett got the feeling that the Doctor wasn’t one to go back anywhere. He was constantly on the run – going back was too painful. He gave a last nod of farewell. “Take care.” With that, he turned and headed into the TARDIS. With a roll of her eyes, River followed him.

SCENEBREAK

As the Doctor threw the TARDIS into the Time Vortex, he finally seemed to notice River glaring at him. “What?” He finally asked.

His wife rolled his eyes. “You’re an idiot, you know that?”

“I am not!” His voice got squeaky with indignation.

“They saved our necks back there.”

“Yeah, and I offered to let them come, didn’t I? But they said no. That’s not my fault!” The Time Lord protested.

River rolled her eyes again. “Not forever, no. This is their home. But they should get one trip, shouldn’t they? Just one to say thanks?”

The Doctor looked thoughtful. “But what if they say no?”

His wife gave him a knowing smile. “Believe me, they won’t.”

The alien started in surprise, then turned to look at his wife curiously. “Have you met them with me before?”

River just flashed a smirk and uttered the word he hated; “Spoilers.”

With that, she activated her vortex manipulator. As she was zapped back into Stormcage, she thought about that memory from those years ago. She’d only seen them briefly that one time, so it hadn’t occurred to her when she’d met them here that they were the same people. But the last few days had brought the memory back to mind, and now she was sure it was them. The two the Doctor had brought with him on that adventure she’d seen only a part of.

One she’d weasel the full story out of him one day.

SCENEBREAK

Castle and Beckett had watched the TARDIS disappear in silence, hands still tightly gripped. Castle knew that Beckett didn’t regret turning the Doctor down any more than he did, but there was still that itch of curiosity. What must it be like out there, anywhere in the past, future, or all of space? A thousand possible stories sprang to his head, but he knew that none of them could ever be better than the truth.

They had just turned to head home when a familiar _vworpp, vworpp_ sounded behind them. The partners turned back to see the TARDIS fading into view again behind them. When it had fully materializing, the door swung over, the Doctor poking his head out again. “Oh, come on, just one trip. One thank-you trip, then back home, safe and sound.” He retreated back into the TARDIS, leaving the door open behind them. A choice.

Beckett and Castle shared a look, questioning and eager. They could both read the answer in each others' faces. Hands still gripped tightly, they pushed past the doors into the TARDIS, closing them behind them.

One trip, then back home. One story to remember for all time.

**Notes for the Chapter:**

> So this is it. The story's over. And all eleven chapters written in nineteen days. I think that's some kind of record for me, I never write this fast.
> 
> I hope you all liked this story. I tried to make the mystery interesting and the OCs fleshed out.
> 
> And I hope you guys will like the sequel I'm planning, whenever I get around to it. Yes, I'm planning a sequel. I didn't want to say anything before because that would have given away that the Doctor was going to ask Castle and Beckett to come with him. However, I don't know what that sequel's going to be about yet, so I'm open to suggestions. They get one trip, so where should they go? Past, future, or alien planet? Or some combination? Let me know what you think. I probably won't get to it for a bit, as I have to figure out a plot and everything, but I'll try to get to it soon-ish.
> 
> Until then, enjoy this actually finished story, and comment if you liked it. :)


End file.
